Fallout 3 and Oblivion have the best replay value and will give you the biggest bang for your buck.

COD world at war has an all right story line, but it has zombies, ZOMBIES MAN! me and my GF play that almost every night, ZOMBIES that is.

my roommate has been playing blade-storm 100 year war lately.

Prototype for some people i guess, i didn’t really like it, but i know some people who swear by it. I find it is too much like Spider-man, actually what was the difference, oh yea you could consume people and transform into almost anyone you saw. Oh and you get a few cool shape-shifting powers, but very repetitive and TOO EASY!

inFamous i hear is amazing, i still yet to play it however.

MGS4, Saints row, oh and there are plenty of PSN games out there that i hear are pretty good.

My biggest recommends are of course my first two Fallout 3 and Oblivion!