Since Modern Warfare is completely boring, and no modern weaponry interests me whatsoever, I hated CoD4 (also attributed to the fact that it was a terrible game).
CoD5, on the other hand - is an awesome game.
CoD6 had better be WW2, maybe Vietnam, or maybe even Future Warfare (o.O) otherwise I won't be buying it.
Nothing wrong with copying near perfection, also known as the CoD3 XBL Multiplayer.
CoD4 was just.. bleurgh. No.
CoD5, is awesome. I'm not looking forward to Infinity Ward making another one, though. They'll probably screw up the series again like they did with CoD4.