I've hardly played any... these are all I've got and I'd say...
1) Fallout 3. Rich map, interesting story and interactions, loads of opportunities with it.
2) Grand Theft Auto IV. Same as the above, really.
3) Assassins Creed: Revelations - the graphics
the missions are a little repetitive but I just love how much detail's put in.
4) L.A. Noire. Love the whole idea of it, really. Would like to be able to personalise the storyline though.
5) Fallout: New Vegas. The desert's quite bleak but I liked the extras and improvements on F3... just not the story.
6) Saints Row: The Third -
craziness. A little short though.
7) Mortal Kombat - lots of gore, fun story mode, great selection of characters
8) Viva Pinata - I don't even care it was fun okay
9) Saints Row 2 - haven't played it so much yet.
10) Gran Turismo...5 I think... meh.
11) Fifa 10. Well just make everything impossible why don't you.
yeah I need more games. I've played a couple of others with my brother's Xbox or at a friend's house but I just counted the ones I have.