Half Life & Half Life 2 are two of the best FPS ever made, totally engrossing. You really felt like you were part of something big.
If a game can get you apprehensive about what's around the next corner then it's a thumbs up from me.
One of the biggest laughs I've had game wise was 'The Getaway'. The dark humour in that was brilliant.
Best sports game ever was ESPN NFL 2K5.