Orange Box is definite, since you haven't already played HL2 and Episode 1, you also get Episode 2, TF2, and Portal, just those 3 are worth the price. (i'm giving my "gift" hl2 and episode 1 to a coworker lol).
I'm a fan of UT and i'm getting it soon (sometime after Crysis).
Don't bother with Farcry, well unless you find it, it's usually like 5-10$.
I nearly fell asleep playing GoW on the xbox, maybe I was tired.. it's got great graphics and lots of gore and blood..
CoD no comment, just not my type.