UPDATED: I got a PS3 now and now my favourite 5 games have changed quite a bit.

5. Gears of War 2

4. LittleBigPlanet

3. Fallout 3

2. Left 4 Dead

1. Metal Gear Solid 4

Note that these are for the games I've played - no others. This is also my opinion based on much I've enjoyed these titles, so if anyone does read this and disagrees, that's fine.