Having such reliance on aiming is a pretty big turnoff for a lot of players. Having aim assist on consoles makes it much more strategic, much more about where you stand, what weapons you use, how you move around, what your teammates are doing, the choices you make, etc. It also lets you see everything the game has to offer without remaining pretty casual.
Not everyone is a hardcore gamer, raum
I'm a PC gamer at heart but I can still enjoy modern warfare 2 on Xbox.
(although I think 3rd person games like assassins creed and prototype are much better suited to pad based games).