I don't necessarily hate Halo, or Call of Duty, they're pretty alright, functional, and such, I just think they're incredibly overrated compared to other better online multiplayer games like Team Fortress 2, Bad Company 2, and others. Also, at least those games aren't as populated by total douches like Halo and Call of Duty.
Although Call of Duty is better than Halo in terms of gameplay, the community is by far worse, especially with all the glitching done there. Halo simply has annoying 12 year olds, but all they do is throw a ***** fit and leave. An excessively annoying ***** fit, but still ignorable if you wisely use the mute button. In the CoD community however, all of the glitchers just ruin the experience big time, regardless of whether you mute them or not.