The Dark Knight The film's big problem is the inclusion of the Joker. It should have been about Batman and Harvey Two-Face, and their similar origins in attempting to fight crime but driven to violence due to trauma. It should have finished with the two putting aside their differences and working together.
Fight Club The revelation that the protagonist and Tyler Durden are the same person is shocking - to anyone who hasn't seen a film since 1973. A better ending would be to reveal that the protagonist is actually the same person as Marla Singer, which unlike the hacky plot that we ended up with is both novel and supported by the subtext.
They're both just gimmicky trailer bait. Particularly the Joker - pretty much all his scenes in the film are included wholesale in trailers. He exists in the film so as the writers can do whatever the hell they want under the brand of 'chaos' as though that's ever been an actual thing in the trilogy or comics (not that 'stuff blowing up' is really a reasonable exploration of chaos as an idea anyway). Two-face turning vigilante in a contrasting way to Batman should have been the central theme of the story.
Wasn't the movie originally supposed to be broken into two but due to Ledger's death they had to cram the Two-face part in at the end of the first? Might explain why it wasn't such a focal point of the movie.
