Story is definitely original. Am liking it a fair bit, although I did notice difficulty was a step up from MW:2, probably because of infinite respawning enemies. The graphics aren't up to the standard of MW:2 either, which was a bit of an immersion killer. I'd probably get more of the stuff with Reznov if I'd played WaW properly, but it's still quite good.
MW:2 was much cleaner, much clearer. Black Ops is very much a 'gritty' game, hell, you'll feel the dirt when you're playing. Make sure you play this one with the sound up as well, or you'll miss the good bits. Has a bit of a Treyarch feel about the story when it comes to cutscenes, looked like an extension of what they did in WaW, from what I remember about it.
My personal preference is IW's 'style', but I'm reserving judgment for the end.