What game should i pre-order for xbox 360?

i wanna pre-order a game for 360 but idk which to pre-order because there is a lot of good ones it looks like. Im thinking of either.... Fallout 3, Gears of War 2, Too Human, Mercenaries 2 World in Flames or Call of Duty 5. if you can think of any other games tell me. Please give me an explanation of why i should get the game. thanks