Gears of War 2
It goes without sayings that Gears of War 2 is a great game. Epic has taken Gears of War and improved every aspect that could have used some tweaking, added a whole pile of new enemies, weapons, game modes, and completely changed the landscape. At the same time, expanding Unreal Engine 3's capabilities to allow for bigger and more brutal battles. Gears of War 2 steps it up a notch on every level, and just like its predecessor, will remain in my collection indefinitely.