The Dark Knight Rises' biggest flaw is that it's pretty much two movies that have been combined. Like in Batman Begins and The Dark Knight, Bruce Wayne faces a "crisis of faith" and wonders if he should continue being The Batman, even more so since he has been retired as The Batman for eight years. TDKR goes through a similar arc more than once (though quite differently) and it feels... weird, is the word, I think. The transition between the two different parts is very well done, but the final act feels like it would be more at home in The Avengers than it is in TDKR.
By themselves, the two parts are amazing, but putting them together doesn't completely work.
For the most part, that's it's flaw. TDKR tries to be a bit too many things, but by the ending it pulls it all together and makes it work.
So, the characters: Alfred Pennyworth (Caine) and Lucius Fox (Freeman) have stayed fairly constant throughout the trilogy, though they both have some character arcs in TDKR, Alfred especially. Christian Bale is still great as Batman, and the "Batman voice" is at it's best.
Closer to the other side of the scale is Bane's (Hardy) voice; his posh voice makes is near perfect from a thematic standpoint, but the audience is listening to the audio (duh) and that's where it doesn't really work. His voice doesn't fit well in the movie as a villain's voice, and it can be heard to understand at times, though he is understandable during the important parts.
That's Bane's main problem; as the villain for this movie, he is fantastic; he's the sophisticated, brilliant, and vicious brute, and fans of the comic should know what one of his important actions will be. Unfortunately , he had to fill the hole left by Heath Ledger's Joker; he isn't that good, but he's close.
Anne Hathaway is damn good as Selina Kyle, and not just because of her looks. She pulls of the 'femme fatale' type of character very well and gives her character real depth.
Joseph Gordon Levitt is great as John Blake, and Gary Oldman is still a fantastic actor playing the fantastic character of James Gordon.
So, how is it compared to The Avengers? That's a really tough question because they are two very, very different movies. It's like trying to compare happy, action packed, fantastical apples to dark, thought-provoking, realistic oranges. You can't really do it. So, we compare them to themselves.
Yeah, that doesn't sound like it makes sense, but here is what the comparison boils down to: The Avengers was better at being an apple than TDKR was at being an orange.
Putting it all together: TDKR is not as good as The Avengers or The Dark Knight, but it's behind them by a hair. It has some flaws, but its good parts far outweigh them.
Personally, The Avengers and The Dark Knight are both 10/10's in their own genres, and TDKR is a 9.5. It is a really great movie and a really great ending to a fantastic trilogy.