Iron Man 2 is highly entertaining. As a stand alone movie it's great. As a sequel? It's less great, but still OK. I feel like instead of Iron Man 2, it should have been called Iron Man Again.
Robert Downey Jr IS Tony Stark. If he ever decided to stop playing this character, Paramount would have a very difficult time getting an audience to accept another actor in the role. There was a lot of controversy surrounding the casting of Don Cheadle to replace Terrance Howard, and I have to say, it was pretty unnecessary. Cheadle's performance is flat and boring and while Howard wasn't much better, there's something to be said for keeping the cast intact.
I'll never understand why Paramount executives would have hired Jon Favereau to direct a major superhero summer blockbuster. The majority of his work consists of comedies and family fare. He started off as a comedic actor which is probably why the movie is so entertaining. There isn't a whole lot of action (probably the same amount as was in the first installment) and yet I was smiling and having fun throughout. The experiences that came from the director's roots in comedy really help keep the audience engaged.
As entertaining, well written, acted and directed it was, Iron Man 2 doesn't do anything to move the characters or the story forward. It really didn't need to be made and so as a sequel, it leaves a lot to be desired. That doesn't mean you won't have a blast watching it. Iron Man 2 is a great way to start off the summer season.