That was the point. It was the alter ego of a Detroit-galvanized, rock-bottom bad seed born Marshall Mathers. Mathers begat Eminem, who himself conceived the maniacal Shady, who spurred Mather's evolution from consecrated underground battle champ to international icon.
For a sub-generation who went from Wu-Tang to Rawkus Records, Slim Shady offered another possible detour. He was capable of being both hard-core and humorous, serious and scatological; the dirty rotten rhymer on underground Soundbombing collaborations and Missy Elliot deep cuts. Along with Jay-Z, Eminem effectively shattered the arbitrary divides that had heretofore cleaved underground rap from the mainstream.
Even those who don't find the latter claim true have to admit that the two, at the very least, caused kids to question what exactly was so bad with mainstream rap. After all, Eminem was on Interscope and was arguably more lyrical and more entertaining than anything simmering in the subterranean.
A decade later, Eminem's "Recovery," the most commercially successful rap album of 2010, served arguably as a flash point for some of the problems ailing major-label rap. Although artistically uncompromising efforts still slip through the cracks (Waka Flocka Flame, Rick Ross, Big Boi, the Roots), rare is the album that escapes from the major-label world that doesn't sound intensely focus-grouped.