Yeah, I think you are right about the Halo effect. That series has certainly wowed a lot of people, and it probably helped bump other FPS's like CoD up for Xbox owners. So when CoD 4 came out, not only did it blow the top off of the previous CoD sales, but it also competed with the big daddy, Halo 3. Now there seems to be a divide between Halo fans and CoD fans, but yeah, it's pretty amazing at how well FPS's do on the 360.