I love this movie.
Its about a trinity. Three heroes working to bring Gotham out of the darkness. Gordon, Dent, and Wayne are flawed heroes. They work tirelessly and nearly acheive victory several times. Its also about a monster. An insane genius, Joker is just as determined to plunge Gotham into madness.
My favorite scene is the press confrence, where Wayne was surrounded by his "adoring fans" as they turned on Dent and demanded Batman's head on a pike. It showed that Joker turn people against their heroes. It was realistic.
However, the heroes stuck together, and even though they work outside of each others knowledge, they trust each other to do the right thing. It paid off and the Joker was caught. Victory was fleeting as Joker is a mastermind.
In the end, the trinity is broken. Two of them cannot work together and the other one, the best of them, is dead. Joker wins.