Mass Effect 1 & 2 are excellent games
Splinter Cell (my favourite game series)
Nier - really under-rated, easily my contender for GotY last year
Started playing Dragon Age and it seems a good investment too
Arcade wise...
Super Meat Boy - addictive puzzle game
Beyond good and Evil - not enought people played this the first time around
Doritos Crsh Course - Free and easily keeps you entertained
Hamrs Way - same as above