I have to say, I'm a bit surprised by the negative reaction. I mean...I've played several COD games, at least in single player, and they're all pretty much the same. The "quick time" events have become more common in later games, but other than that, it's pretty much the same thing over and over and did I mention over again?
The single player has always been extremely linear and driven by "set piece" battles. The multiplayer, from what I hear, has been extremely popular but largely untouched formula-wise for a while now.
But really, what else would you expect? What kind of innovation were people looking for? I also can't help but wonder how negative the reviews would be if there was some radical innovation in the game. "ZOMG! I wanted COD, not [insert other game that was copied here]!!"
I think what this highlights is the fact that the series is basically done at this point, and done to death. Activision has been pumping these games out, what, annually? Sometimes two a year? How many times can you buy the same game with no real improvements? When people say "It's a glorified map pack," I wonder whether they thought the same of BLOPS or MW2 or MW1 or COD3 or whatever. I mean, admittedly, MW1 shifted from the WW2 scenario, and BLOPS shifted to 1960s (although, I gather, with marginal success), but these games have been single player interactive movies for years now, and the multiplayer has been pretty formulaic for years now, so...aren't they all just basically map packs? Isn't that why folks get into these games?
Admittedly, I didn't pay attention to the prerelease hype, so I don't know how much of this is disappointment at specific promised features being missing, but really...why is any of this surprising people?