hmm, I just finished the single-player campaign for the first time -- I've never played any COD game before, and I just bought this because it was kinda cheap in the store.
For all the hype, it seemed a bit lame. The campaign took all of about 4 hours to complete, with a muddled, uncompelling, plot that skipped all over the place in way that felt like they were just checking stuff off a list ("snow mission?" check "desert mission?" check ...). It felt like a random recycling of scenes from Michael Bay movies. There was never any real sense of "place."
Within each mission, although the graphics were pretty nice (an impressive number of polygons being pushed around!), the enemies felt very very shallow, compared to games such as RE5 and Uncharted; even in the latter were quite static, always spawning enemies in the same place, with the same behavior, there was a certain responsiveness that made them feel somehow more "there" than the enemies in MW2. The MW2 enemies, even though they were shooting at me, always seemed sort of like they were animatronic robots on the other side of a glass wall or something.
As set pieces, they were often impressively complex, but never really all that interesting; almost always they felt like a series of rooms (even many places that weren't actually rooms felt that way) to be cleared one by one.
Even the widely commented-upon "terrorist" scene was just sort of stupid -- it's really kind of hard to be shocked at what's going on when it all feels so completely artificial.
It's interesting to compare with Uncharted 2, as that was similarly highly scripted and linear, and had a somewhat jumpy plot. There's no real contest I think -- Uncharted 2 was hands down a better game: a better, much longer, plot that, while no less ridiculous, was more coherent and at least interesting; more compelling and personable characters (despite being stereotypes); much better enemy AI; significantly better graphics; much more immersive, and ... simply a lot more fun.
Anyway, I feel vaguely like I wasted my money. I think I'll go play Uncharted 2 again...