graphics don't mean stuff, and neither does engine
cod uses idtech, which is the best engine
the engine means worlds of difference in terms of graphics, capabilities, and sometimes gameplay - games that run on quake engine tend to have very twitchy controls (star trek voyager for example).
idtech is hardly the best engine around - it's extremely old (small environments, mediocre graphics). imo the best engine is unreal engine, as it's very scalable, easily serves any purpose, and looks damn good.