First off, let me say this...I loved both movie. This is not meant to offend the directors or say which director is better than the other. This is simply a fun competition between two equally amazing films. Enjoy!
Iron Man, directed by Jon Favreau, is about a billionaire industrialist who is captured over seas while demonstrating a new weapon. He narrowly escapes and has an epiphany. He becomes the hero Iron Man and faces terrorists and evil within his own company.
The Dark Knight, directed by Christopher Nolan, is about a superhero who faces his greatest enemy while he questions why he does his "work" at all.
Jon did a great job adapting a classic hero onto screen. He made sure that Iron Man followed as close to the feel as the comic as possible. He also made sure that he had cast the perfect person for Tony Stark. Favreau really did his homework on this one. Nolan had already established Batman in Batman Begins, so he made sure that he focused on Joker and Two-Face for this one. He knew that people wanted a realistic Joker, so he studied many of the graphic novels featuring the darker Joker, while keeping you guessing as to what his origin is.
Who is the winner you ask? Well, I'll tell you that there is no winner. Iron Man and The Dark Knight are on two different leagues. Iron Man follows the comics more closely than Dark Knight, but The Dark Knight was more about making a really good filmmakers movie. So, I say that Iron Man wins when it comes to staying true to the material, but The Dark Knight wins when it comes to reinventing the material. You tell me in the comments below which one you believe is the better honor.