I think you can have a great film in any genre. I think people should judge each one on its merits, rather than lumping them all together and assuming they are all the same. As you would with any other kind of film. Some are good, some bad, some great etc.
TDK is a great film IMO and being a Superhero/Comic book film shouldn't detract from that.
I think part of the problem is people dismiss the source material, which is a shame. Some of the story telling and writing in comic books is superb.