Wallace, definitely. I went through a phase where my fan-girling for him had almost religious proportions. I'd definitly rank Infinite Jest among the most transformative reading experiences in my life. Of course that puts me in a certain category of DFW-fan which is easily mockable (it's the kind of preference you shouldn't admit to on dating profiles for instance, if you want to appeal to women at least, as it causes almost as much wariness as professed love for Bukowski, Pahlaniuk or the Beats).
Still, I think everyone who cares about literature should at least be able to see the appeal (even if it may not have much personal resonance or if over-identification with the characters might be a bit of a problem). I'm fairly confident that after the hype, the backslash and the backslash to the backslash, his relevance will persist.
Franzen however... eh. I found him readable enough, so I would probably co-sign your attestation of basic competence, but I've never met someone who's getting all starry-eyed about him. He generally doesn't evoke too much passion - rarely among his defenders, and, I would argue, not even among his detractors, who often focus more on his old-man-yells-at-cloud stick in his essays and other public pronouncements than his actual work. (My beef is that he mostly just affirms a view of the world already pretty familiar to me; he captures that accurately and there's probably some value in that alone, but it's not exactly an under-represented perspective on things; so far there hasn't been anything particularly eye-opening to me about reading him. And as far as mere elegance of prose goes, I like McEwan better.)
Anyone vouching for Junot Diaz? I haven't yet come around to reading him, but I've heard some good things.