Perhaps I shouldn't have said "only". But Eminem presents himself as a gangsta, and while he does cover a lot of his own issues, he doesn't strike me as particularly introspective. I'm not necessarily preferring one guy over the other here--I'd much rather listen to OutKast or Mos Def than either Eminem or Kanye--but I think Kanye's merger of the traditional content of a lot of singer-songwriters with hip-hop is what makes him stand out.