The most skillful, moving rap I've heard is by Eminem: "Lose Yourself." I cannot claim to have heard a wide range of the songs in that style. It is no more a product of my generation than Bing Crosby or Louis Armstrong. Nonetheless, I can appreciate the artistry of Bing, Louis, or Eminem on those occasions that I do hear their work. And I'm hardly alone in liking "Lose Yourself." It received five Grammy nominations and an Academy Award.
Interestingly, my favourite living poet, Seamus Heaney--73 years old, white, Irish, and a Nobel Prize winner so another unlikely fan (statistically speaking)-- also thinks that Eminem is an artist to respect.
Rap as we know it may have begun with gangsters, just as Blues came from the Southern Black underclass, jazz began in brothels and rock and roll was thought of as a sign of moral collapse. But music styles, in general, seem to bubble up from the bottom of society. The same with dance: the samba from workers in Rio, the tango from the outskirts of Buenos Aires, the flamenco, in part, from Gypsies. Those who study and teach about cultural expressions are not, on the whole, those who make them.