This has nothing to do with auto aim, if you turn off CoD auto aim you can still aim and hit whatever the hell you want (if your good enough). In KZ2 you cannot (well maybe if you practice alooooot) because the game has acceleration on the right stick movement.
accelerated movement really ruins the day for alot of gamers, because it has to be completely relearned for each induvidual game.
If you want to have a good aim in KZ2 you gotta learn how much the game accelerates your aim when you use [x] angle on the right stick. Unless you learn this, you will overcompensate every time you aim. It can be learned, sure, but it requires a whole more time than having not accelerated movement (or atleast having this acceleration on a smaller scale). There are many many good console FPS games where i can go from either one of them and have "perfect" aim. (as good as i can aim - not actually perfect) I can instantly aim for peoples heads and lead them and kill them. And then there is KZ2, Far Cry 2 and PD:Z. In which my aim for some reason is waaaaaaay off what it usually is. Now, FC2 may be because of bad framerate, but KZ2 and PD:Z is because they both use accelerated aiming.