Mario Kart is a great game, although it can be infuriating at times. I hate it when the computer 'cheats' (or it feels like it does). I have a graveyard of broken games controllers thanks to that game.
I think I must have played just about every version of Mario Kart (apart from the DS version). Not sure which is my favourite... Probably the original N64 version or the Game Cube (Double Dash) version. Anyway, you can't go wrong with mario.
Dragon Age: Origins. Superb game. Fantastic storytelling - let down slightly by some dodgy game balancing. (Mages are far too overpowered.) I didn't play the expansion but I understand that it is very good.