This is the kind of inquiry that usually pisses me off (it's s'posed to be about the music, no?), but for fun I spent the morning listening to hip-hop on headphones, and I cannot tell a lie: Many of my faves don't sound that great, genius sh-t like Paul's Boutique included (Edit: this is the original CD, not the remaster mentioned above). As someone already pointed out, the production on The Roots's records is pretty exemplary (especially Phrenology and The Tipping Point), and that carries over to Common's Like Water For Chocolate, which ?uestlove produced. (Ditto for Be, production by Kanye West…and yes, that means Kanye's records sound good, too, much as I hate to say it.). OutKast's records sounded fine, even back when they were broke.
Some things truly surprised me, though:
De La Soul - Art Official Intelligence: Mosaic Thump and AOI: Bionix
Tricky - Maxinquaye
The Miseducation of Lauryn Hill
M.I.A. - Arular
Sway - This Is My Demo
Mr. Lif - I Phantom (the interesting thing about this one is that it toys with the idea of being alterna- and lo-fi, kinda like when the DJ tells him, "You get what you pay for," and Lif replies, "Well, dawg, I ain't got much.")