Unless Nolan at some point decided to shoot a 22 slug in the creative portion of his brain. Then yes it will be a "Deeper" movie. None of the marvel studios have come close to the depth and attention to quality of the Nolan Batman movies. Narration, dialogue, imagery, pacing. Nolan's batman movie are just superior in all departments. Except the aforementioned accessibility portion K4tz mentioned.
Simply put, they are better "super-hero"movies (sorry marvel fanboys).
Plus as far as depth goes the avengers is pretty low on that scale. As I've said in my first comment on the movie. It was good, fun. It's a light movie that fulfills a long time geek dream. The story's depth as well as the dialogue and acting were nothing to write home about.
The downside to this is that from a critical perspective. The geek dream fulfilled is blindsiding fans to the movie's critical flaws that prevent it from making that leap from good to GREAT!
Was avengers bad, hell no! It was fun, an above average super-hero movie leveraging action and light entertainment as it's key tools to succeed.
The Dark Knight succeeded where no other super-hero movies ever did. It managed to actually be completely accurate to what Batman is supposed to be to long time fans of the character, come in with an engrossing story and characters and top it off with epic action to keep everyone happy.
The sad thing about this is that depth and accessibility are a very difficult balance to strike, even more if you want to make the push from Good to AWESOME. This is why so many movies make a butt load of money without actually being anything special or new. Because you go too far on depth and most people just won't be able to get into the movie. Most movie goers aren't looking for anything more then 2 hours and a half to shut off their brains and see explosions, tits and jokes (massive commercial success of Micheal Bay movies anyone?
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This is not to say that being that kind of movie goers is exactly wrong. But it means that when money starts being counted, accessibility is a much better movie seat filler then depth. Because there are a lot more people who are of the type seen above then anything else.