Personally, I find the stories have a restrained feel about them, a sameness in tone (and in coloring palette) that seems to be what marks a comics work as "literary" for people accustomed to prose. I've been getting on of those dreaded creative writing MFAs for the past couple of years, so I can't pretend to have anything against literary fiction, whether it be in prose or in comics form. I think it's unreasonable to expect the literary establishment to take notice of something like Street Angel or Scott Pilgrim when a work like that is not of the genre they cover, though one might criticize more broadly the lack of diversity in the books the mainstream literary media tends to cover.
Then again, comics like Street Angel don't have an equivalent in prose form; they are the kind of stories that don't exist anywhere else but in comics and would probably not work as prose. Coverage and recognition of this type of work is lacking in the mainstream media, and, from what I understand, under-represented (or not represented at all) in anthologies like The Best American Comics. (Criticism of that anthology follows much in the same line as criticism of other books in that series, such as The Best American Short Stories or The Best American Essays -- the works included tend to be of the same genre and reflect the tastes of the editors. This is just the nature of anthologies, but I think it's the "THE BEST" part of the title that gets people's hackles up.) I think what those of us interested in this in comics hope and will try to bring about is that the literary establishment recognizes comics for the unique medium they are and not only when they conform to the genre of "literary fiction" as it has been codified by the literary-intellectual complex (I'm thinking publishers-critics-universities here).
Heidi MacDonald discussed this in a post on her blog The Beat (this link goes to a follow-up to the initial post, which is linked to in the entry) that got roundly whupped all over by some people who seemed sort of pissed off by it. (Tom Spurgeon of The Comics Reporter and Christopher Butcher of Comics212, specifically.) I thought the focus of the post wasn't quite what it could be, a unifying thesis being unclear, and the arguments weren't well-supported, but, man, I didn't get angry about it. (And that's something, considering I get angry at something as trifling as that damned "magic screen" Sprint commercial and am started to get annoyed by people who capitalize the "de" in my last name.) And I didn't get all Modern Language Association on it like one of the commenters, who actually used the word "normative" in a reply to it. Some people just don't get the "use language appropriate to the setting" thing.
But I'm getting far afield.
I took the post it as an impetus to think about what underlies Heidi's frustration at what is recognized in comics. There is great diversity in the kind of stories told, but only the far ends of the spectrum are generally known outside of the industry and fanbase -- there are the literary comics covered by the literary media and the superhero comics covered by the pop culture media who are more interested in the movies based on the comics than the comics themselves.
Some of the commenters in the Guardian post linked to above (they're an amusing bunch. I tried to get involved in the thread I link to, only to get annoyed and frustrated. You should see when they decide to discuss Americans) seem to think that the great, unrecognized middle is a good thing. Creativity can thrive when there is no critical eye cast on it, I suppose the thinking is. But I believe this means, as I said before, that what comics do uniquely and better than any other medium is what goes unrecognized, and it sure as hell is a shame, isn't it? Personally, I see no reason to elevate "underground" comics any more than I see a reason to elevate "literary" comics -- I want to judge on merit, as my tastes understands it, and I want others to do the same. But one can't judge what one doesn't know about.