As gamers, we all have our own personal pantheon of gaming gods: experiences that shaped our virtual lives, those magic moments that take our breath away, those beautifully realised alternate worlds that captured our imaginations, characters that captured our hearts and addictive titles that captured our spare change at the arcade. These are the games that spring unbidden into our minds as we drift off to sleep, inspire us in our own creative endeavours, and are the things we gush about breathlessly to anyone who will listen when we talk about the hobby we love. Our beloved games will vary from player to player, but some games transcend individual opinion and find their way into the hallowed halls of the collective consciousness as brilliant, must-play, near-perfect gaming ambrosia. And one game that touched almost everyone who played it in some profound way was System Shock 2.

System Shock 2 was a genre-busting title before people had even realised that gaming had genres to bust: it was survival-horror, action-adventure, first-person shooter and role-playing game all in one marvellous package. But above all that, what System Shock 2 did was tell you a story. It told a story in a way very few games had ever tried to do; it engaged those who wanted to be engaged, and let anyone who didn't disregard whatever they wanted and get on with the action. Or the exploring. Or the role-playing. So when Ken Levine and the team at Irrational Games (renamed about 8½ minutes ago to 2K Boston and 2K Australia, no doubt so all the praise falls on the 2K brand-name!) announced BioShock, the spiritual successor to the System Shock titles, you could almost hear a million gamers worldwide gasp in collective excitement.

Well, now it's finally here. BioShock debuts on Xbox 360, a mere 8 years after System Shock 2 graced our CRT monitors back in 1999, but the millennial shift could not be clearer. It takes all the raw materials that made System Shock 2 so brilliant and refines them, purifying the base compounds and spinning almost pure gold on a console that has had an awfully large share of lead lately. But don't be put off by all this talk of System Shock 2 and gushing hyperbole; BioShock stands on its own two feet and does not require you to have played the System Shock games. Hell, they took place in outer space, whereas BioShock, well...

BioShock begins with you on an airplane, circa early 1960. Mum and dad have given you a present but before you can open it, the plane crashes and you're the only survivor, treading water amidst the wreckage with no land in sight besides a lighthouse in the middle of nowhere. But this isn't some weird episode of LOST where you'll have to carve out a new society and survive against the elements, because somebody has already done it for you – beneath the waves, in the darkest depths of the ocean lies the city of Rapture. A place where there are "no gods or kings, only man.” Your descent into rapture is the sort of textbook game introduction that will no doubt become a fixture of university degrees in game design in years to come; a limited interactivity ride in a Bathysphere that sets the surreal scene, and also introduces you to the conflict and gives you a new purpose: surviving and escaping.

Andrew Ryan introduces you to Rapture, his magnum opus, through a grainy film reel that denounces post-war, post-New Deal America, Communist Russia and modern religion, all of whom claim ownership of the sweat off a man's brow. Rapture is a place where the great will not be constrained by the weak, where petty morality will not shackle advancement and where the best and brightest can toil towards whatever endeavour they please. Yet something has gone terribly awry in Rapture – you will see an innocent citizen slaughtered before you even leave the bathysphere. Indeed, within the first five minutes of play, it will become apparent to you that BioShock is a game with themes and issues that go far beyond what we have come to expect from our interactive entertainment. Indeed, you should expect to have more than just your twitch-reflexes challenged by BioShock, because this is a game that has more emotional impact than any first-person shooter on the Xbox 360.

And the key to this success is the city of Rapture itself, which is without a doubt the most important character in the whole story. From the moment the doors of your Bathysphere and a mysterious Irishman named Atlas offers you his help, you will be overwhelmed by Rapture. This sense of awe and wonderment will never leave you, not even during your darkest hours or the most intense of battles. Rapture tells you more of the story than any mission briefing or character monologue ever could. The narrative reveals itself to you in every splash of blood, every piece of ruined furniture, every propaganda poster and every advertisement. Sure, players so inclined can barrel past it all with the grim determination junkie seeking their next fix, but to do so will cause you to miss half of the experience that BioShock offers.

While the carnage all around you tells its own tale, audio tape recordings from many of Rapture's citizens illuminate the events that have come before you far more explicitly than the environment itself. These messages from beyond the grave are an effective and chilling storytelling method and using them to fill yourself in on Rapture's history is one of the highlights of the game. Levine and his team have perfected this technique that they pioneered with System Shock, and these disembodied voices become far more important people to you than any flesh and blood character you see on the screen ever could. It's a fact BioShock exploits both ruthlessly and humorously, as more often than not you will get to meet these people...or what's left of them, anyway.

By now you're probably thinking that BioShock sounds like a pretty immersive adventure or role-playing game, but are wondering what happened to all the cool weapons and abilities you heard about. Well breathe easy because this is still a major part of the BioShock experience. Much of the reason Rapture has gone to hell stems from the discovery of a benign little sea-slug whose slimy skin contains a genetic Pandora's Box they call ADAM. Unstable stem-cells – the building blocks of our body – within the slugs can be manipulated for all manner of purposes: rejuvenation, regeneration, and most dangerously, modification. Of course like anything there's a cost involved: physical and mental instability, and the need for a bigger "hit” of ADAM to get the same effect as your body adjusts to it.

Virtually every enemy you encounter in the game is a "Splicer”, someone who has genetically enhanced themselves with an ADAM solution of some sort, become addicted or unbalanced, and eventually as society beneath the sea crumbled, lost the plot entirely. They wander the halls mumbling to themselves, talking to their dead babies, tirading at the husbands who left them or reassuring themselves that the stockmarket will bounce back next quarter. It's pitiable and unnerving, but when they start swinging improvised weapons at you or unloading a pistol in your direction, you've got no other choice but to take them out. And BioShock is not a game you could ever accuse of having a shortage of options in this department!

Conventional weapons will form the backbone of your arsenal; starting with a meaty looking wrench for melee fracas, and then gradually expanding to period-authentic genre favourites like revolvers, shotguns and tommy-guns. Things get a little more experimental from here on in: there's a chemical thrower with the ability to spew fire, ice or electricity, an improvised-looking grenade launcher, and a crossbow that can fire normal bolts or set up electrified tripwires to slow down any pursuers you might have. Each of these weapons (excluding the wrench) have two or three upgrades that can be acquired on your travels through Rapture, and like everything else in the game, you have complete freedom as to which modifications you select when you reach a Power To The People upgrade station. All of the updates physically affect the appearance of your weapon which is a wonderful touch, and they serve to make your arsenal look even weirder and more experimental.

But standard firepower will only get you so far in Rapture. Its denizens have made the most of the ADAM phenomenon to give themselves an edge, so it's only fair that you jump on board the genetic engineering bandwagon too, right? Tissue tinkering comes in two forms in BioShock: active abilities called Plasmids, and passive abilities called Gene Tonics. Plasmids are the real heavy-hitters here, and include nifty tricks like snap-freezing enemies, spontaneously combusting foes from across the room, shooting bolts of lighting from your fingertips and telekinesis, which allows you to send incoming grenades express post return-to-sender. There's a wealth of less offensive Plasmids too, which can be used to surreptitiously tag splicers so security systems go nuts and take them down with prejudice, enrage foes to attack each other, and even command one of the giant Big Daddy creatures to defend you. Or you could just launch a swarm of bees from your flesh to harass your foes. Gives new meaning to having "hives”, that's for sure!

These active abilities consume Eve, an enigmatic cocktail that supercharges your senses and allows you to muster the energy to activate your supernatural skills. Cynics may call in "mana for your spells”, but either way it's an essential item for any proficient Plasmid practitioner. Not so for any Gene tonics you imbibe, which simply become part of your basic genetic structure and require not external energy source to use. These are divided into tracks: physical, which deals with specific physiological changes such as toughened skin for damage resistance; combat, which can allow you to swing your wrench and run faster; and engineering, which deals specifically with hacking and inventing. All told there is just over 50 Gene Tonics and almost a dozen Plasmids available, and you can have up to six Plasmids and six tonics in each track at any given time if you buy the upgrades to allow it. If you want to cycle them out that's cool too, all you need to do is locate one of the many Gene Bank stations scattered across Rapture.

What you can't do is refund the ADAM you obtain during the game - once you spend it on Plasmids, Tonics or extra slots; you're stuck with the choice. This makes your encounters with the creepy Little Sisters all the more important. These eerie children were once normal girls - mostly orphans - that have been genetically modified to store and grow ADAM for the rapacious population of Rapture. They can be found wandering the empty halls of the city harvesting what ADAM they can from the dead with giant syringes, never far from the armoured protection of a Big Daddy. If you manage to take down one of these formidable foes, you have the choice to either harvest the little sister, or rescue her. The former kills the poor thing and nets you the maximum possible ADAM, the latter returns her to some semblance of normal but yields half the amount of ADAM. It's a tough moral dilemma, one compounded by the enigmatic Dr. Tenenbaum who promises you great rewards if you help her little ones rather than killing them.

Indeed, one of the things Levine and the team at Irrationa...er, 2K Australia/Boston really wanted to improve in BioShock was choice: giving the player more of it, but not punishing them for making them. Not only can you pick weapon upgrades as you please to suit your implement of choice and switch up your Plasmid and Gene Tonic combinations at will, but you will never once be asked to do any of those nasty Role-Playing Game class decisions. In BioShock you can shoot your way through, go Plasmid-heavy, use the security systems to your advantages by hacking, or any combination thereof; whatever it takes to keep you alive. This allows you to tailor BioShock to your own style of play in an even less restrictive manner than Bethesda's critically acclaimed Oblivion, and it means that FPS nuts, role-playing fanatics or even absolute newbies can jump right in and enjoy themselves.

Arguably, this is something of a double-edged sword in terms of game design. BioShock has made many concessions to the mass-market that die-hard System Shock 2 fans would scoff at: weapons never break or jam, there's an abundance of everything if you're willing to scrounge, combat is simple and has auto-aim on by default, and there is no real penalty for dying either. BioShock doesn't utilise checkpoints per se, rather a VitaChamber that rebirths your character if you should fall in battle. These are abundant within Rapture and you'll rarely have to travel for more than a minute or two to get back to where you carked it.

This is all well and good, but it really makes the game feel a little bit too easy at times, and at the very least takes the edge of the horror and tension they have striven to create because nothing is fatal, and the odds are almost always on your side. You can make it harder on yourself by turning off in-game hints and the objective compass that points the way, as well as disabling auto-aim or increasing the difficulty to hard. But there's always this nagging feeling that you are invincible and untouchable, and this dilutes the otherwise gripping narrative and spooky atmosphere that so few games manage to create.

However the other concessions are almost all good: the user interface is pure minimalist, communicating everything you need to know as simply as possible; the controls translate perfectly to the 360 controller; and there's no inventory management to worry about. This isn't quibble free though: you can't easily check what Gene Tonics you have equipped or available, there's no way to check on your invention components and the only way to know if you need ammo for a gun is to equip it and select the ammo type. Yes, it sounds like nitpicking, but during your 20-30 hour adventure, having to trek to a gene bank/ammo vendor/U-Invent station will fast become one of the most annoying things about the game.

BioShock has many other depths that this review does not plumb: there's hacking mini-games, the ability to take research photos to find your enemies weakspot (and yes, for massive damage!), items that you can invent to save yourself money and much more. But half the fun of the game is discovering these things on your own and either getting involved or ignoring it if you aren't interested. So much like story elements, we won't spoil anything for you. Suffice to say that BioShock can either be a fairly short game if you charge through it like you were playing some generic shooter, or it could take you ages to explore every nook and cranny and milk every last secret out of Rapture.

And there is absolutely no reason not to want to do that, because BioShock is an absolutely gorgeous looking and sounding game. Special mention should be made of Garry Schyman's orchestral score, which works in perfect harmony with licensed golden oldie tracks like Bobby Darin's "Beyond the Sea” or Pattie Page's "How Much is that Doggie in the Window.” It sets the scene so perfectly that your bathysphere ride down to Rapture is like stepping into a time-warp and emerging at the cusp of the 1960s. The voice acting is precision perfect, and the audio logs in particular do a marvellous job of bringing the game to life. Ambient noises and sound effects aren't left behind either, and playing this game late at night with a Dolby Digital 5.1 surround sound setup is downright frightening.

Of course the visual design plays an even bigger role in creating the world of Rapture, and BioShock is truly astonishing in this regard. To say it is dripping with atmosphere is hardly extraneous hyperbole, because the game literally is dripping much of the time! Water plays a huge role in the game as one could well imagine it would in a leaky undersea community, but the way the Unreal Engine 3 handles the tricky substance is impressive, and it conveys dampness in a way virtual worlds never have before. The lighting is superb, and the use of shadows to create abject terror in the player is worthy of an award on its own.

But like Gears of War before it, visual perfection eludes BioShock for much the same reason it did that other graphical tour de force: the UE3 engine. BioShock often struggles to load textures in a timely manner when you transition rapidly between areas, often leaving corpses and minor objects unskinned or missing the normal mapping that gives them realism. Usually this corrects itself quickly, but other times it takes minutes or does not happen at all. There are also ominous reports of the game freezing for 5-10 seconds after many hours of continuous play and recurring frequently as you continue, which is not something we experienced first hand, but is still cause for concern.

Ultimately though, even these glitches and bugs cannot detract from the masterpiece that is BioShock: even the most famous artworks have some flaws, and this game is no exception. There is just so much to love here that a second playthrough doesn't feel like a chore – it feels like something you need to do to appreciate the game in all its glory. Of course you can snag almost all the Achievements in one run through if that's what you're after, and they're a good mixture of story-based objectives and exploration/completionist rewards. There's two possible endings of course, and like everything else about BioShock, the choice is yours as to which you will pursue and whether you will endeavour to experience both. But either way, the impact of this game is not something you will easily forget.