There's nothing realistic about the gameplay in any of these, with the possible exception of Operation Flashpoint, and only that, because you have to traverse fairly long distances and it's pretty easy to get killed by one shot from a guy you never saw. Otherwise, the maps, weapon damage, audio, and AI are all tuned to be fun, not realistic. If it were realistic, you'd have limited ammo, not shoot very often, an when the shooting started, you'd get pwned immediately because you're fighting trained fighters and you're a noob.
To draw a driving analogy, "realistic" would be like sitting in a full-size F1 simulator and going against Michael Schumacher every single time. Every time you turned it on, you'd lose and not by a little bit either.