What Xbox 360 game should I get next ?

Halo, Halo 2, Fable, Fable 2, Guitar Hero, Guitar Hero 2, Guitar Hero 3, Guitar Hero Aerosmith, Guitar Hero Metallica, Guitar Hero World Tour, Rock Band, Rock Band 2, Call of duty World at War, asins Creed, Bioshock, Fallout 3, Left for Dead, Dead Space, Saints Row 2, Tom Clancy's End War, Gears of War, Gears of War 2. There are more, but i dont feel like listing them all.