Here is a list of notable exclusives/console exclusives from last year. I'm not sure if your interested in Kinect so I wont list any games for its for it.
Metro 2033 was one of the more underrated games released last year.
Alan Wake is one of my favorite games this gen.
Halo: Reach is a must buy.
Fable 3 is a good game, not as good as Fable 2, but still a good game non the less. I would just buy fable 2 now and wait for Fable 3 to be cheaper.
SC: Conviction was pretty damn fun. The single player was short, but sweet. Spec-ops with a friend is a blast.
Deadly Preminition is considered a cult classic. I would check it out.
Crackdown 2 was a fun game. Wait till it's cheaper if you decide to buy it.
This year exclusives and console exclusives...
Gears of war Triple pack (includes gears 1,2 and all DLC for gears 2).
Gears of war 3
X-com
Forza 4
Rumor: Halo: CE remake
Codename: Kingdoms (might release in 2012)
You cannot forget about all the amazing xbla games this year like hybrid, Mrs. Splosion man, torchlight, Class3, beyond good or evil, etc. E3 will have more announcements.