i like better halo 3 but thats cuz i like more non-real games and with impossible structure or possibility of happening than something that can happen, is real, or already happened.
Both were a grave disappointment, in my opinion. Call of Duty 4, because there were really no defining features to the game, excluding the nifty run feature (by pressing in the control stick). Halo 3, since I had just finished Bioshock, one of the greatest games for the Xbox 360.
Cod4 is better because it is different and more realistic also I love the steady sniping thing where you don't have to hold your breathe and all Halo3 has is grav hammer and couple things newer like maps and thats it. I love Cod4!!!