Robert Downey, Jr. (Sherlock Holmes 2009, The Avengers 2012)
Don Cheadle (Hotel Rwanda 2004, The Avengers 2012)
Gwyneth Paltrow (Two Lovers 2008, Don't Let Me Down 2010)
Scarlett Johansson (The Prestige 2006, The Avengers 2012)
Sam Rockwell (The Green Mile 1999, Cowboys and Aliens 2011)
Samuel L. Jackson (Snakes on a Plane 2006, The Avengers 2012)
Mickey Rourke (The Wrestler 2008, The Expendables 2010)
I liked the first one better, but Iron Man 2 definitely can hold its own against other super-hero movies.
Downey, Jr. reprised his "born-to-play" role with more attitude and cavalier than in the first movie. He once again contributed something new and welcomed to the Iron Man legacy.
Different from the first movie, Iron Man 2 wasn't the expected battle against terrorism. This one seemed more "Hancock-ish", with our hero battling himself as much as villians.
And what awesome villians there were! The United States Gov't (Garry Shandling never had a chance), Sam Rockwell (sort of a Lex Luther's witty cousin type), and the ever-impressive and show-stealing Mickey Rourke as he plays Whiplash--the smaller-time Iron Man villian who is the primary villian in this story.
Whenever Rourke was on screen I was enthralled. After seeing The Wrestler I'll never doubt Rourke's abilities as an actor (not to mention Killshot and Sin City).
Overall, I liked this movie a LOT.
Factoid: Terrence Howard was slotted to reprise his role as Tony Stark's best friend and ally Rhodey, a.k.a. "War Machine." However, after demanding pay equivalent to Downey, Jr.'s, the film-makers replaced him with Academy Award-winner Don Cheadle. Cheadle was happy to play the role for less money than Terrence Howard (who'd only claim to fame is Iron man) had demanded.
In short, this is the worst case of an actor "blowing it" that I've ever heard of. His short-sightedness, however, didn't stop him from landing the role of Nelson Mandela (A politician ranked among legends like Thomas Jefferson, Ben Franklin, and Winston Churchill) in the 2011 film Winnie.