From Screen Rant..

Rating: 9/10 (14 November 2010)

For me, 3.5 out of 5 translates into 7 out of 10, and no, I can't agree with that — I'd have to give this beast a 5 out of 5. Actually, a 9 out of 10, losing 1 point because it was only incredibly entertaining and had a plot line that held together. But, getting that 10, is hard.
THERE WILL BE SPOILERS
but I want to say this first! The acting was picture-perfect. This reminds me of Richard Donner's post-production remark, in gist: "I guess Marlon Brando was worth the money." Perhaps I shouldn't put quotes around that, but that is what he meant. It pays to have talent and these people so earned. I agree, a half-naked Whiplash didn't seem believable — Favreau and Rourke MADE it believable. The burning underneath relationship between fickle Tony and over-burdened Potts was believable. I really didn't believe Scarlet could pull off Black Widow.. but, boy, oh boy, did she pull off Black Widow, leaving me wanting more. I so wish I could say that about the former Spider-Man series! And, then there is Sam Rockwell's smarmy Stark competition, Justin Hammer.. very well played, sir. Sam is going places. We first saw him as the sneak in Charlie's Angels playing the victim to be revealed as the espionage snake, I saw him help beat a drug-wasted art celebrity to near unconsciousness in Basquiat. He's clearly doing things, be it Moon or otherwise. Very nice interplay within the cast. And Cheadle came through for us as the seamless replacement. Lessening my concern over the Edward Norton / Mark Ruffalo affair. Director Favreau, Happy, Foggy Nelson, +1, when are you going to return to your role in Dare Devil, I miss you (and that cast)!
IT'S COMING
and then there is the tiny role of Nick Fury.. actually, I am disappointed with the one-eyed Jackson in this. Maybe he isn't being given enough room to role but Marvel should have went with the original image.. no sense of Nick's toughness here.. I really hope he changes this in the Nick Fury Movie, if that ever happens.
THE SPOILERS
but blink and that is really a very small part. I loved the timing and the story here. IM2 supersedes 1!! And as I say this I know there are other opinions: the hard-ass action all the way folks won't agree. Fine. Look at the story: Iron Man's dad has a greater vision but his creative partner in the formulation of the ark reactor did too. In a sense, Iron Man is Howard Stark's creation but Whiplash was his partner's. There is the idea of connectivity and karma here: what goes around, comes around.. sins of the fathers kind of thing.. not developed enough to bring that solid 10 out of 10 but close. And Whiplash is brilliant and not dead at the end of the flick either. Captain America's unexplained shield. And, Thor's hammer. All on a time-line preceding The Incredible Hulk.
I also loved the idea that Tony was dying from essentially metal poisoning via the battery implant (the alcoholic gig just wasn't palatable), that SHIELD is aware of it, and that Tony has issues with his past relationship with his father. Nice writing there! Frankly, Batman TDK does not hold up to this cinema. The writing, the acting, the film-making is better here. I really hope this is not Marvel's highest peak but just the start of a sustained plateau. Film-making is getting smarter.