Click here to listen to USC professor, literacy expert, and, oddly, current rabble-rouser Stephen Krashen talk about language acquisition , pleasure reading (or narrow reading), and academic discourse. Right before the 21 minute mark, he begins talking about his love for comics and respect for their importance in his own literacy development:
"For me... it was comic books, and I gotta confess, it's still comic books.... Batman, Superman....What a wonderful foundation that gave us for higher levels of literacy, and we treated it as literature...."
He then talks about having Stan Lee taking him to lunch -- and paying! :)
Continuing on, he says, "I've never gotten over comic books. There's nothing like a new graphic novel."
His basic thesis is that language acquisition, especially academic language acquisition, is best facilitated by lots of reading in the forms and genres that you love best.
Krashen's synthesis on many studies and writings on comics and reading in The Power of Reading should be among the first things comics-and-literacy scholars read, in my opinion.