I don't think comparing two summer blockbusters about comic book heroes from the two prominent publishing competitors is unreasonable.
That being said, I think in some regards the comparison loses merit. The Avengers is not quite mindless, but on a far inferior intellectual level of TDKR. I've said before, Nolan's last picture was nominated for Best Picture and Best Original Screenplay. Whedon created Buffy.
The Avengers is an excuse to bring Iron Man, Hulk, Cap, and Thor into one movie to tear New York City apart. TDKR is a conclusion of seven years of developing relationships that test the fabric of civil liberties, parenthood, and self-examination.
So I don't know what the point of comparing a tense thriller about a revolution to a quirky 90 minutes of explosions and crumbling buildings.
Who says? And why? Because it won't have a socio-political commentary? Doesn't mean it's less intelligent. Simply means it isn't bothered about socio-political commentary and reminding people how **** the real world is.
If the characters are written well, and the story is written well, which I imagine it will be, considering it's a Joss Whedon penned script, then I fail to see how it is less intelligent than TDKR.
The story of Steve Rogers, man out of time, coming to terms with the fact his friends and family and loved ones are all dead, has the potential to be just as compelling as a story about Batman, probably more so actually.
Or how about Tony Stark, billionaire playboy, developing an inferiority complex over the living legend that is Steve Rogers?
Or how about Bruce Banner coming to terms with the beast inside him, realising that he can be a force for good in the world and that he isn't a freak.
Or how about Thor, brother of the enemy, not wanting anyone else to harm him and being conflicted on how to deal with him.
All these bits of characterisation,
if done well, shouldn't be looked down upon.