I loved Avengers dearly, but DKR was on a completely different level.
Avengers is more of a simple man's movie. Lots of bright lights, action, simple man's plot, colorful, awesome superheros, witty and comic-like lines.
The Dark Knight is is more of a complex man's movie. Deep plot starring a character that had 3 movies to fully develop, brilliant script, fight scenes were further in between but epic, gritty and felt more like something was on the line, some of the greatest quotes in movie history.....
I'll remember some of the shyt Bane and Batman said in TDKR for the rest of my life. I don't feel the same about Avengers....all I remember is "Puny god..." and "We have a HULK!"
Also TDKR was far more high stakes....people LEGITIMATELY felt Batman could die. More was on the line. Despite Avengers being more of a "fight for the planet" type of situation, there was never a time where you said "Jeez....Thor might not make it."
At the end of the day, I give Avengers a A- and TDKR a A+...for I am a complex man and TDKR suits my taste more. I predicted nikkas whose attention spans and simpleton ways of thinking and observing entertainment wouldn't appreciate TDKR's 2 hour and 45 minute brilliance and would make a crazy topic like this though.