Oblivion, Star Wars: Force Unleashed (with the DLC, can't wait for the new stuff though), CoD4, Halo 3, and various sports games. Currently working on CoD5, Batman: Arkham Asylum, Wolfenstein, Fallout 3, and Madden 10. It'll be awhile before any of those are actually completed though
So far i have got: COD 2 *hated Hill 400 on Vet mode* COD 4, Clive barkers Jericho *i really enjoyed it :P* Dead Space and Resident evil 5. I have NFS most wanted to do but aient got rounf to it. im nearly done with gears 2. need to get max level and seriously 2.0 and complete all 50 waves on horde *normally and on the Nowhere map. Never have the time to do all 50 online so been doin wave 40-49 solo* Before the DLC came out i was a few achievments off Cod WaW.
its actually get 80 with everyone, and its actually really easy to do. but it does take a few hours. the hardest achievements in the game is the dueling with duane.... that is just a headache.
NFS Most Wanted, which is kind of sad because that was one of the first games out for the 360, so you got all 1000 just by completing the game. I've come close in some others, but no cigar.
I got it on Halo 3, Skate 2, and I believe that's it. Halo 3, only for the armor. Skate 2, because that game is awesome. I usually don't care too much about achievements. If they look too hard to get I won't bother. Haha.
Probably going to have Dynasty Warriors 5 empires in the next few days, it froze on me last night right before i got one, so i have to redo quite a bit on it. NFSMW is going to be there soon, only a few more races.