Crysis works fine on win7 64 bit. With Crysis 2 coming out in a few months, Crysis and Crysis Warhead are dirt cheap. They're both really good games, however the original Crysis is the better for story. They're a bit short, I remember thinking to myself when watching the final cutscene for the first time "HELL YEAH! THIS GAME IS AWESOME", only to then watch the credits roll and realise there was nothing more.
Definitely buy it. Will only set you back $10-$20 depending where you buy it from.
GTA IV is a good game if you haven't already played it, as well as the EFLC. GTA IV is just one of those iconic classic games. Can get it with the EFLC for around about $30-$40 (give or take a bit, depending where you buy from). About 20 hours gameplay + 5-10 hours each for TLAD & TBOGT.