Promise is possibly the most powerful weapon in videogames. The promise and possibilities that a title like BioShock dangles tantalisingly in front of us keeps us all hanging on in there, keeps us believing, keeps us pre-ordering. Even when the shelves are awash with me-too pap, cheap knock-off licensed fodder and hyped sequels, a title like this stands out like a beacon of hope amid a sea of mediocrity. No pressure.

But we all know from long experience that promise can be a bitter curse - one destined to magnify any minor disappointments when we finally get the game out of the cellophane and fire it up. A game is never as good as its hype, or so history seems to rub in our face over and over again. Some of us even try our best to avoid getting caught up in the hype bubble, so that, for once, we can actually be pleasantly surprised about how good something is without having it rammed down our throats by hysterical marketing and frothing commentators. Believe me, even as a reviewer - especially as a reviewer - you're always on your guard when it comes to the Next Big Thing. Disappointment comes practically gift wrapped for your displeasure.

So to have any shred of doubt surrounding BioShock comprehensively swept away within the first ten minutes, well, you feel like dancing. You want to tell people about this game who you know won't even care, just because it makes you so giddy inside. Before we get into the nitty gritty, here's the deal: Bioshock doesn't just meet your expectations, but completely redefines them forever in ways you never even expected - in ways that games used to in the past, routinely. The hours spent playing this masterpiece were the perfect encapsulation of why videogaming is such a favourite waste of time for so many of us. Thrilling, terrifying, moving, confusing, amusing, compelling, and very very dark. BioShock isn't simply the sign of gaming realising its true cinematic potential, but one where a game straddles so many entertainment art forms so expertly that it's the best demonstration yet how flexible this medium can be. It's no longer just another shooter wrapped up in a pretty game engine, but a story that exists and unfolds inside the most convincing and elaborate and artistic game world ever conceived. It just so happens to require you to move the narrative along with your own carefully and personally defined actions. Active entertainment versus passive: I know which I prefer.

Screen shots can't even hope to do the game justice.

The kicker is that for about 80 per cent of the time spent playing BioShock, you have absolutely no idea who you are or why you're even there. As players of the celebrated 360 demo will know by now, you're a castaway involved in a plane crash. You're in the sea. It's the middle of the night. There's floating burning debris all around you. And, oh look, there's a mysterious structure that just happens to be sticking out of the water with an entrance. What are the chances? Rather than bobbing in the ocean dying of hypothermia questioning this conundrum, you swim over, clamber out and head inside. It seemed like a good idea at the time.