cod was originally derived from medal of honor which was a dam good game back then. Allied Assault was the first fps I played.
a group of devs from moh did not like the direction they were taking with the game as the protagonist being the awesome hero all the time.
They preferred a more helpless soldier in the heat of war point of view.
They succeeded with their first cod game but the others seem to just take the same stance as moh now.
You could mass produce cod games, which in my opinion is exactly what they are doing now.