Call of Duty isn't a game - you press a button and a helicopter appears out of nowhere to reduce men to mangled messes. How is that entertainment? You aren't stimulating your brain - the scientifically-proven point of games - you're stomping around a grim, depressing world doing grim, depressing things in the name of "fun". It is the equivalent of turning on your TV to watch war footage, and enjoying it.
Nothing has ever frightened me (me) more than when I've come across some thirteen-year-olds discussing the tactical advantages of one gun over another.