I absolutely LOVED Elder Scrolls IV: Oblivion, but other than that I haven't really found a lot of good games for it. Eternal Sonata (based on the dying dream of Chopin) is not so much fun as really odd. Tetris is a good generic multiplayer (especially if you set it to "send lines" to other players! :D) but the backgrounds for the 360 version are really annoying.
DUImonkey
gears of war 1,2 condemned 2 had decent multiplayer but is more of a single player bioshock (single) also castle crashers from XBLA but i would stear clear of COD 4 its multiplayer is populated by a bunch of under 10 kids who curse alot and seem to think there all MLG's but COD Waw has nazi zombies which is pretty cool i know theres some more but i cannot for the life of me think of them
Urza12
thanks for the ideas, i'll be sure to think about it. I just got 3 games for it recently, Devil may cry 4, Darksector, and Battlefield: Bad Company