In his nicely balanced review of The Dark Knight Rises, The Guardian's Peter Bradshaw labels the film Wagnerian ('a superhero Bayreuth'). I think that this is an apt description of the film. No doubt its length (two and three-quarter hours) and various apocalyptic themes from apocalypse to heroes self-sacrificing and labouring in moral quandary justify this comparison on their own.
In addition, there is a technical but entirely appreciable way in which The Dark Knight Rises may be said to resemble a Wagnerian music drama. Wagner himself said that the most valuable part of his art was that of transition, from moving from one thought, mood or scene to another. Consequently his music doesn't always have clear arrival points. Rather it moves from one moment of tension or imbalance directly to another. Settling is deferred. Like a musical treadmill you can't help being carried forward. Wagner's goal was the propagation of unendliche melodie or never-ending melody, where the tune meanders like a stream of consciousness (Inception, anyone?).
Similarly Christopher Nolan's approach to editing has visuals, music and the dramatic sensibility overlapping. The original score composer, Hans Zimmer has a not-insignificant hand in this by writing self-perpetuating music. Feeding one another, tipping the next sequence of events off, informing the action not only of the moment at hand but of previous action, this tumbling causality keeps the temperature in motion - in fact this very mix of metaphors, climate and dynamism, though apparently oxymoronic, is precisely the character of opera, of any multi-faceted art form.
Nolan's great achievement in The Dark Knight Rises is that he manages this continual, homogenising imbalance consistently across the full span of this long film, a genuinely Wagnerian achievement, if only in stylistic terms. The downside is that it's a bit like a trying to read an extremely long sentence that sounds well-composed as you read it, but as it never finishes, one grasps neither its conclusion nor its basic argument. This, in addition to the widely reported inaudibility of the film means that its point is cut adrift of its patina, and risks leave the audience invigorated but unedified.