I don't know how one can hate on Eminem 99-03, dude was a classic emcee.
Bars, some of the funniest and illest stories, flows, technique, freestyles, comedy, fukk the establishment approach, charisma and all that good shyt even did some social criticism and . Yes he's been ass for over a decade, yes he's huge cause he's white, yes his fans are unbelievably corny but remove all that, he was a A1 emcee in his prime, top 20 of all times.
As far as pure spitting, probably the song posted above Infinite or Role Model.