Halo3. I played CO4 for a solid month straight and didn't even touch Halo. But one day I was playing, and I realized I wasn't enjoying the game anymore. I put it down and started playing H3 again, and started having fun again. (one thing i realized when going back to H3 was its poor frame-rate... play cod then go back to h3 its so choppy feeling). Call of Duty just didn't hold my interest the way Halo does.