For one reason, no headglitching in Halo 4. Bungie made a genius design choice to lower the target reticule starting with Halo 2. This forces you to expose your whole frakken head in order to shoot behind cover.
Shame on Treyarch for not correcting this fundamental problem.
Halo 4 is just the same as its predacessors with new enemies.
This statement basically shows that you are a CoD fanboy, who knows nothing about Halo. If anything, people are complaining that the mechanics changed too much.
Keep in mind that I enjoy both games. It seems weird that I have to make this qualifying statement, but it is what it is.
Actually I am not. I only play Call of Duty to get away from the RPG genre for two to three weeks a year. But I know people out there who think that the Halo series rises not just above all FPS but all games in general and compares all games to Halo.