C.O.D.?.?.?.?.

I'm just posting this because I was playing COD 4 at Andreas's {i'm not that good he owned me 40-80 :( } and I noticed how much it had improved since the original. So when is enough, enough? (COD 8 may be the last) and what should they add to the newest Call of Duty to make it worthg buying??? VOTE ON THE POLLS !!!!!!!!!!!!!!!!!!!