Number 8: Portal 2

I was a bit late on the Portal bandwagon. By the time I got a "true" next-gen console this year (The Wii doesn't count, kids) I'd long since missed Valve's The Orange Box, the undisputed star of which was the original Portal. Developed using the Half Life 2 engine, Portal was a quirky and charming puzzle game centered around the use of a level-bending portal gun. It delighted players in 2007, and since then people had been asking for more. Well this year we got more, and it was even better than we could have hoped.

A sequel to Portal could've been an easy thing to put together. Most fans would have settled for a few new levels, maybe a new gimmick or two. It wasn't exactly a formula that would benefit from too many changes. Such a well-balanced game can't be messed with too much, otherwise you risk alienating the existing fan-base while failing to bring anyone new in. Lucky for us, Valve did a fantastic job making Portal 2.

Maintaining the same tight puzzle/shooter mechanics as its predecessor, Portal 2 carries on the darkly comic sci-fi plot with predictable aplomb. You wake up in a decayed Aperture labs, where you soon realise that GlaDOS (the first game's wonderfully cutting AI antagonist) is back in control, and out to avenge her previous defeat. Joined by a bumbling robot sidekick Wheatly, impeccably voiced by Stephen Merchant, you're tasked with solving more devious puzzle rooms with the eponymous portal gun. But of course, the plot is secondary. As with the first, what really matters is the incredibly intuitive and addictive gameplay.

And boy does it not disappoint. From start to finish each puzzle room presents a perfect little challenge, so much so that you'll find yourself saying "just one more" for hours and hours on end. Gimmick-wise Portal 2 adds to the returning cubes, turrets, and pressure pads of the first game. Hard light bridges and anti-grav gel bring an extra mind bending twist to the action, and the single player campaign benefits from it. But it's in the online multiplayer that Portal 2 really shines.

Bringing a whole new set of levels to the mix, the co-op is easily Valve's best addition to Portal 2. The puzzles require you to work together as a team, but that'll quickly go out the window in favour of screwing over your opposite number in as many hilarious ways as possible. Why simply offer them a bridge over a batch of poisonous water when you can take it away while they're half way across it? If you're looking for a theme in this list so far, "fun multiplayer mode" seems to be a good candidate.

Following up on a game as tightly designed and perfectly paced as Portal was never going to be easy, but Valve have made it seem like the most natural thing in the world. At a time when the concept of game sequels is reaching saturation point (have we really had four Assassins Creed titles in as many years?), Portal 2 was a refreshingly creative and enjoyable experience. It never deviates far from its near-perfect source concept, but brings in just enough new content to make it fee necessary. Dare we hope for the same with Portal 3?