The form of "The Straight Story" is simple: an old, frail man who does not give up on his long journey to see his brother again. A simple, but all the more touching road movie.
Batman himself only plays a limited role. Focus more on politics. That's an interesting approach and what makes the trilogy what it is. But what else is there to lose in a film about which everything has already been said.
The Dark Knight lives from its numerous moments of suspense, which Nolan really takes to the extreme here. Some is so bitter and hard to swallow. It doesn't happen that often in movies, which I really appreciate.