2p2 Help me choose my new video game!

[TheSalche]

So because I care about grades this semester, I'm limiting myself to buying one more game before winter break. Currently I've been playing lots of Halo 3 and Orange Box and enjoying both of them. As for my general tastes in games I love shooters, but I do also dabble in other games like Splinter Cell, KOTOR1 & 2, Diablo 2, SupremeCommander, C&C3 and GTA: San Andreas.

From what I can tell, my choices are:
1. CoD4
2. Crysis
3. Mass Effect
4. Super Mario Galaxy
5. Assassin's Creed
6. Kane and Lynch: Dead Men
7. UT3

Obviously I have a 360, Wii and a decent PC (4600+ AMD dual-core, ATI X1950XT 256 mb, 2 gigs of decent ram, running XP).

So 2p2 ... help me out!