In a recent interview with MTV Nicolas Cage volunteered his acting skills as 'any' super villain in the next Batman 3 movie. He didn't know which one he wanted to portray, he just knew he wanted to be in it. This is exactly why he should not be in it.
Why should any storyteller hire an actor that doesn't understand the material or appreciate a character. Remember when Nicolas Cage was almost cast as Superman? Look at how hallow he was in GhostRider! Sure the movie was poorly constructed but Nicolas Cage hasn't been great in a movie since Raising Arizona. Meanwhile the importance of picking a performer for a role is what is paramount in super hero movies. Why? Because in super hero movies you as an audience member are asked (not expected) to suspend disbelief. The believability of the characters especially the antagonist and protagonist are perhaps more important than everything else including special effects and set design.
When an actor asks to be in a super hero movie for the sake of being in it the producers give up respect for the story and thus the graphic novel audience gives up respect for the story. Comic book readers are unlike any other book reader. Take for instance that you don't see people discussing who should play Tyler Durden on web sites prior the filming of Fight Club because traditional books are not scrutinized by the public for who is acceptable or even expected in an a role. Why? Because you can't compare comic book stories transitioning into film the same way as traditional books are.
When any comic book becomes a movie, the run up includes fan boys posting and cross posting wide and detailed discussions on who should play who in the subsequent story. The Internet discussion of X-men demanded that Patrick Stewart play Xavier. When the film brought him to the role, there was a wave of relief among every potential X-Men viewer that would come to see the film. This goes on for many characters (heroes and villans alike) that ended up on the big screen.
Sure it's a little bit silly to think that comic books and super hero stories are so highly scrutinized by their fan base, but it is what it is. Hollywood has done well in the past to realize this reality exists. When it fails to accept this principle, you can almost define the box office sales by the pre-Internet discussions going on before the films are released. As an aside, comic book readers don't like to see big name Hollywood stars in MOST super hero movies. They want to see the actor that most looks like their character in the story. They want to see an actor that has the mannerisms and feel for the character in the story. They want to see an actor that is most like the character, they never want to see an actor playing the character. This is why it is so hard for Hollywood to make a good super hero movie. A rare exception is Robert Downey Jr. as Iron Man and even he had to not be more like Robert Downey Jr. and more like Tony Stark.
In the case of Nicolas Cage, when an actor doesn't step up and ask for a specific role because they identify or appreciate a character, they really have no business asking in the first place. Nicolas Cage doesn't belong in Batman 3 or any super hero movie as long as he doesn't have an appreciation for a character in it. If Nicolas Cage were to have said to MTV, "I would like to play a villain in a super hero movie some time" this would not have been offensive, but to people that read comics his current interest is an insult.
Comic book readers watch characters they know and appreciate come to life on the big screen by way of Hollywood studio heads that hold no respect for those characters often enough that I felt it best I defend comic book readers today. After all, I am one of those readers.