I won an XBOX360, so list me must haves.

[SageClock]

Xbox
Blur
Catherine
Civilization Revolution
Dead Rising 1 or 2
Deus Ex: Revolution
Ghostbusters
Overlord
Project Gotham Racing 4
Prince of Persia

I used to be a big XBLA guy though, here's the ones I thought were good:

XBLA
Jet Set Radio (just came out)

Age of Booty
Battlefield 1943
Beyond Good & Evil HD
Braid
Castle Crashers
Castlevania Symphony of the Night
Carcassonne
Catan
Chime
Geometry Wars 2
Half-Minute Hero
Ilomilo
Limbo
Lumines Live
N+
Outland
Pac-Man Championship Edition DX
Pinball Arcade
Rez HD
Scott Pilgrim
Shadow Complex (if you only try one, make it this one)
Space Invaders Extreme
Spelunky
Splosion Man
Super Meat Boy
Ticket to Ride
Torchlight
Toy Soldiers
Trials Evolution
World of Keflings