Although i wouldn't say its the greatest series ever, certainly a good one, i still think its worthy of being a best seller. It may lack in some areas enough for one to argue that its not the best, but it always does enough to make it worth buying. Activision deserves everything they are getting from the Call of Duty series. My personal favourites... Call of duty 2, which did an excellent job of emulating the WWII atmosphere, and Modern Warfare, which brought an higher level of excitement to the game, modern warfare 2 was great, but it was really just more of the same.