OP: Flawed logic, most sequels are the 'same game' but polished with new shiny things added on for more bling, and thats fine because it works
New campaign, new and improved multiplayer, tweaked gameplay features, new modes, taking what was good from CoD4 and improving it. Don't judge a game you haven't played yet judging from a few videos saying it's the "same".
Exact same arguement for L4D2