Originally Posted by RedIsNotBlue
A few reasons. One, it is one of those films that is just "cool" to hate on. It ties into another reason that TDK was so amazing that anything following it was going to have a hard time keeping up. If the timeline was shifted and TDKR came before TDK then it wouldn't be hated on as much. TDK set the bar so high in terms of how a comic book film should be done that TDKR was sort of doomed from the get go because peoples expectations got way too high.
Having said all that and that I enjoyed TDKR and thought it was a perfect ending to the trilogy....I can see why there is people that didn't like it. It did have problems that are easy targets for people who can't get past nitpicking.
In my opinion TDKR might be the best movie of the three but not the best Batman movie if that makes any sense. The average comic book superfan tends to be very knowledgeable about Batman and most expected a better Bat film. Those of us that are movie super fans could tell good film-making when we saw it, thus making the hate towards it hard to swallow for some of us. Those who disparage TDKR as beign as bad a film as Batman and Robin know next to nothing about film. But they might have a good case on their hands if they dissected why TDKR was a poor end to a Batman series.