This is an interesting discussion topic. What actors were good in their comic book role and which of those ruled.
I think RDJ's Iron Man beats all others by a wide margin.
Yeah I think RDJ's is by far and a way the best with his portrayal of Tony Stark/Iron Man.
Chris Evans I feel did a great job in both his roles as Steve Rogers/Captain (which I thought was a questionable choice at first) and as Johnny Storm/Human Torch.
Edward Norton was superior to Eric Bana in every way when it came to playing both Hulk/Banner. Gonna have to wait and see how the new guys does in the role but I would have preferred Norton to have remained.
Chris Hemsworth was very believable as the Norse Thunder God, I know before they cast him I couldn't think of anyone else that could have pulled of the role.
Hugh Jackman while not exactly looking like Wolverine from the comics, really excelled in the role. Patrick Steward was the only choice to play Prof. X and Ian McKellan was wonderful as Magneto. James McAvoy and Michael Fassbender were also excellent in playing those parts as well.
Wesley Snipes was entertaining as hell playing Blade, Ryan Reynolds was hilarious as Hannibal King, serviceable as Wade Wilson briefly, and god fucking awful as Hal Jordan/Green Lantern.
Halle Berry sucked as Storm, and was dreadful as Catwoman. Nic Cage was a poor choice to play Ghost Rider even though I did enjoy those movie.
Jack was much better than Heath at playing the Joker IMHO, but both were great for the movies they were in. I still think Michael Keaton was the best of all the Batman with Clooney being the worst, and Kilmer and Bale being somewhere in the middle.
Christopher Reeves is the definitive movie version of Superman and I doubt that ever changes. Routh did a good job with what he was given, and I think if the script had been better his performance would have been as well, he just got a raw deal. The new guy looks the part but I still have little interest in the new movie thus far.
Ron Pearlman is the only one that I think comes close to being better that RDJ as far as casting goes, because he was damn near spot on perfect in the role of Hellboy.
Thats all I can think of right now.