Call of Duty 4, and no I do not agree with you on "The two best first person shooters on the Xbox 360." simply because Halo 3 is not a good game. It takes no skill at all to play Halo 3, or any Halo games in a matter of fact. All you do is hop around 50 feet in the air and spray to hopefully hit somebody. The only thing that is keeping it alive is the Forge mode ability. Call of Duty 4 is x10 more realistic than Halo 3. In Halo you can light somebody up with a full clip of Assault Rifle ammo and watch him kill you and walk away. Call of Duty 4 is a good game, but it is certainly not the best, Halo 3 is just no even close.
Halo 3 was fun at first with all the live options. If you would have asked me this 5 months ago i would have said Halo by far. So I kept playing Halo for a long time and then it started to get boring. I started to play it less and less and then I started to get mad at the game cause I started to notice all the glitches. The luck in that game is not fun cause some people got lucky way to much.
I started to play COD 4 and loved it right away with the live and all of the cool weapons. I wish it had multiplayer but it doesn't. There is no luck in that game only skill and strategy. There are some glitches but not a lot. Playing the game was awesome. Once again it started to get boring cause of how much I played it. There was a lot of anticipation for both games and that made them get boring really fast.