Modern Warfare 2 is not nearly as good as the original Modern Warfare...

[Barozi]

The first 1/3 of the camapign is a bit weaker than in CoD4, but the rest is at least equally awesome.
Spec Ops mode is fantastic though. Multiplayer is also a bit better, so overall I'd say it's better than CoD4.
GOTY candidate (My GOTY is AC2 though, no doubt about that)