My Dad Earl said:
Maybe I'm in the minority here, but I think the Joker is the overall winner in the Dark Knight.
Being part of a trilogy, you kind of have to consider the 3 movies together, but a strong argument for good winning can be made in the Dark Knight.
Joker creates chaos, but based on the ferries with the bombs, the people of Gotham were fundamentally good, even when the Joker created a perfect scenario for them to be selfish.
Wayne makes a morally ambiguous decision in creating the sonar network, but then redeems himself when he hands over the power to Fox and allows the network to be destroyed once it served its purpose.
Batman ends the movie on the run for Dent's death, but it was by choice and allowed Dent's fall from grace to serve a greater purpose.
The Joker gets some punches in, but the bad guy got captured and proven wrong about human nature, the big overarching plan of making Dent fall from grace in the public eye failed.
If you add The Dark Knight Rises, Batman saves the city again, and Bruce Wayne gets his happy ending.