Eminem is popular not because his lyrics are violent or because he is white (though both do contribute to his fame and his controversial status), but because he has flow. He can write meaningful rhymes and then deliver them. Does he express ugly ideas? All the time, but he expresses them well. I've written previously about my reverence for language. Rap, at its best, shows how evocative the spoken word can be, whether it's Biggie setting the standard for Ghetto Fabulous in "Big Poppa" or "Juicy", Wu-Tang illustrating how "Cash Rules Everything Around Me" or Will Smith lamenting that "Parents Just Don't Understand".
No, the problem is that the art form has become completely commodified and derivative. Sex and violence sells records. So why, as a record exec, would you go beyond that to try and find someone who can, you know, actually rap? Find someone with a suitably gravelly voice and menacing aspect, throw some kind of thick beat down, and print money. If you're lucky you might even get to make a video with chicks in bikinis making come-hither at the camera. Thus, we have such forgettable tripe as Mystikal and...actually I'm having trouble remembering the names of individual acts because there is so little that is individual about them.
Is it any wonder that many of the more distinctive voices are moving away from rap and into business (Jay-Z), 'political commentary' (Kanye), or acting (Ludicris, Andre3000, Sticky Fingaz from Onyx)? Unfortunately, even this "cross-over" is becoming commodified. Witness the 50 Cent blitz going on now, what with movies, CD's and video games. (Spaceballs the Flamethrower, the kids love this one...). It's not an artist, it's a marketing plan. Here's an interesting take on 50 as not so much a paragon, but rather the embodiment of this trend:
Discussions about Fiddy are never really about Fiddy, he acts met[o]nymically for rap at large because he displays no uniqueness. He stands in for rather than out from his genre. He is literally a stereotype, and a wildly successful one at that. In one version of this theory, he plays the part and plays the game to perfection. In another, he is all that is bland and exploitative about rap.(Via Lauren).