Halo is a much better game in my opinion despite the fact that they aren't very comparable. CoD is more of a lone gunman game which requires little to no tact or strategy besides "Get behind the enemy so they can't shoot back" there is little honour or mutual respect in CoD also. CoD all everyone does is yell at each other, in Halo, you have a much more mature fan-base as all of the little children that yell at one another think that CoD is a much better game and will avoid it like it's radio active.
That made me lol. Because kids absolutely hate lasers and aliens. I notic no difference in the community. Sure cod has the occasional squeeker (like any other game) but go and call the people living in their mothers basement mature. My friend recently started playing some old halos again, and the people their deffinetly weren't rated m for mature. No one cares about the ratings anymore, that's kinda bad.