I would get the original Gears of War if you haven't tried it, Naruto: Rise of a Ninja or Naruto: Broken Bond if your a Naruto fan.
Get Call of Duty 4: Modern Warfare instead of Call of Duty: World at War. I heard that Call of Duty 4 has a better online component than Call of Duty: World at War and besides the concept in COD4 is better and more futuristic than CoD: World at War.
And for crying out loud get Halo 3!!
Those are my recommendations.