The problem I have with the Modern Warfare series is their laziness and how they basically gave us PC gamers the finger.
I enjoy playing my Xbox 360 but FPS games are one genre that I just can never enjoy on a console. I'm sure a lot of the gamers out there that are big Modern Warfare fans have probably never played FPS games on a PC and only really "know" the controller, but I could be wrong.
It probably depends on age. There's a legion of people who played PC FPS's when they were at their glory from say 1998-2005, and most everyone I know has abandoned the PC for consoles for a whole host of reasons. The PC still has its advantages but its no longer the only choice for legit online gaming. The 360 kind of changed everything. Someone who wasn't of age back in the quake/CS glory days might not have the same frame of reference, but there was an undeniable paradigm shift of western developers from PC to console in the mid 2000s. And a lot of gamers went with them. PC-only gamers are basically holdouts. Even those leading the charge on PC (dice, valve) take consoles very seriously - but you can still tell that their console products suffer for essentially being PC ports.