Call of Duty 4 by far because of it's leveling up system and prestiege modes are better than those of Halo 3. What most of my friends and myself like about Call of Duty 4 is the ability to choose your own class instead of hunting down weapons like in Halo 3. I just wish that Call of Duty 4 had vehicles like Halo 3 and it's Call of Duty bretheron