Wrong. The best part of the game is MP. I would've been fine if that's all the game was.
Can't argue there.
I've barely played the SP in the various other CODs, but from most of what I hear, this is the same stuff. I don't know what you were expecting.
demi 
I feel like IW was given the ability to make LOUD NOISES!!!! better than they were in WWII, and they sort of overdid it. In a lot of ways. I don't ever remember choke points like cod4 has in cod2. But it's been a while.
Frankly, I don't play SP in any FPSs more than once (well, I don't play any games more than once, really) so I want an experience. From what I've played so far, that's what IW did, even if the gameplay seems somewhat archaic and unfair. If you thought it was too hard, you should've bumped it down a difficulty notch.
But really, I barely play the campaign/story in FPS anymore. The last few I have finished are HL, HL2, Halo co-op, Metroid Prime 1 & 2 and Bioshock. The only one of those that even HAD multiplayer was Halo (MP2 doesn't count). And that's like this entire decade.