A game as a good as Halo for the 360.
From the moment you first chainsaw a drone to when you're running away from a berserker like a madman, Gears of War grabs you by the throat and never lets go untill the bitter end. My only complaint was that the game never did well in explaining the background story, so I kinda found myself a little confused as to what the locusts are and why there are so many different kinds of them. All and all a really great game from start to finish.
(On a side note, how come you never get to fight the Brumak?)