You don't often get much choice in games, because in real loving life you are supposed to follow the damn mission, not wandering around like a richardless twat and running around the map looking for a different way of doing things.
in real life, you can't automagically pick up ammo from guns on the ground. in real life, there's no crosshair on the screen. in real life, one knife slash can't kill you. in real life, your health doesn't regenerate and one bullet will either kill you or wound you enough to no longer be fit for battle. in real life, you have to put your gun away before throwing a grenade. in real life, there are no killstreaks. if you try to make an fps SOOPAR REALISTIKZ, it ends up being an unfun piece of stuff. fps games should be over-the-top in at least one respect and not focus on realism. if you focus on realism in a game, the terrorists have won the war on fun.