Weapons as light as a feather, limited recoil, no jamming, unlimited sprint, perfect vision, completely cramped and linear levels, ability to take multiple gunshot wounds and then just sit in the corner to magically regenerate, and laughably terrible plots with major loopholes does not a "realistic" game make.
If you want to play a shooter for "realism" then try out the ARMA, Delta Force, and Operation Flashpoint series. Even those barely scratch the surface of what actual combat is like, but at least they put some effort into it. Don't even try to label Call of Duty games as "realistic". Doing so is an insult to anyone who has ever served in the armed forces. Realism was never in the developer's mind during the creation process. Having fun, however, was. Any battle in real life is much, much, much, much slower and methodical. Because, believe it or not, humans are not mindless NPCs that run straight into enemy fire and take cover at the same exact spot in the same exact position they just saw their buddies head get blown off at. I know Call of Duty games like to portray otherwise, but most soldiers don't actually want to die.
http://thebrigade.com/2010/12/20/so-ya-think-your-call-of-duty-game-is-intense-heres-the-real-thing-video/ This video isn't a completely accurate depiction of warfare, as it is only one battle and the soldier whose helmet the camera was attached to is being an asshat and running around and firing too close to friendlies.But it's enough to show that Call of Duty doesn't have shit on the real deal.
I don't care if you people argue about which online shooter is the most fun (Bad Company 2, obviously) but please don't bring up realism and video games in the same thought.