I may be 18 but I am a gameaholic. I have had nearly every Nintendo system ever made, going back NES, SNES, N64, Gamecube, and the awfulness that is the Wii. I have a PS3, Xbox 360, no life whatsoever.
For anyone with a 360 though, really consider Left 4 Dead. What a delightful game that is.
Also, if your new to 360 check out:
Mass Effect
Oblivion
Fallout 3
Bioshock
CoD2
Oh and by the way, Lego games kick so much ass. I like the Star Wars one better than the Indy one, but both are so good.
P.S. I know I am an UBER dork.