"The Dark Knight" succeeds where all other comic book movies have failed thus far. Most comic book movies succeed primarily as summer blockbuster popcorn flicks. "The Dark Knight" succeeds as a film.
First of all, Heath Ledger plays the most convincing villain in years. Unlike the performances of several other Batman villains from the past series from the likes of Jim Carey, Tommy Lee Jones, Jack Nicholson, and Arnold schwarzenegger, you never look at his Joker and say "That's Heath Ledger." You say "That's the Joker." His performance also deserves massive amounts of awards.
Christian Bale continues to play the tormented hero. Whilst Bruce Wayne was at first tormented by the fact that his parents died in "Batman Begins", he is now tormented by the fact that he cannot be with the woman that he loves dearly. Add on the massive amount of injuries he sustains every night, and you can understand where maybe he would want to retire sometime in the future.
Rachel Dawes, the woman of Bruce Wayne's life, is now played by Maggie Gyllenhaal. Whilst she does respect the character that Katie Holmes created, she also improves the character. Whilst Katie Holmes could only express her emotions through dialogue, Maggie Gyllenhaal can express her emotions through dialogue, mannerisms, and facial expressions. Basically, Gyllenhaal is a real actress, and Katie Holmes should stick to teen soaps.
Harvey Dent is played by Aaron Eckhart. His performance, whilst less memorable than Heath Ledger's Joker, is definitely still an improvement over past interpretations of Harvey Dent. "Gotham's White Knight" has a genuine fall from grace. It is entertaining to see his character at the beginning of the movie and to see his character at the end of the movie.
Gary Oldman gave another outstanding performance. It is always nice to have this down-to-earth character in the movies. It really makes the movies for me. Whilst Harvey Dent, Bruce Wayne, and The Joker have several big picture ideas, James Gordon has small picture ideas, like protecting his family. That makes his character very sympathetic.
Morgan Freeman and Michael Caine have very small roles in the film. But, their roles are expertly performed. Alfred and Lucius Fox each play male role models in Bruce's life. And, they each help Batman on his quest in their own way. Alfred gives emotional support, and Lucius gives him all those fun gadgets.
Overall, I'd have to say that this movie is the masterpiece of all comic book movies, and also succeeds very well as a crime drama. If you were to change the faces and names of this movie, and turn Batman from a caped crusaders to a private detective who busts criminals (Basically what his job description is anyway), the movie would still make money. That is the difference between a movie that requires a name to sell tickets, and a movie that raises the expectations when you hear that name.