Halo is HIGHLY over rated. I know that if you are going to play halo 3 online, then the community is filled with nothing but people who want to be jerks. However most games are. I never played call of duty 4 online but I have seen my freinds play it online and it seems to me that it would be more entertaining. Call of duty 4 compairing to halo 3, in single player, outranks halo 3 by fact. Halo 3 is filled with mostly videos instead of missions. The acheivements are easier to obtain in call of duty 4 because the majority of halo3 acheivements are online. I personally dis-like all halo games, But as far as the difficulty of the game goes, halo 3 is way easier to beat than call of duty 4. Call of duty 4 is hard and long and I also broke my controller on my tv because of it. If I were you I would get call of duty 4 just because the gameplay is better. Not to mention graphics are way better.