I've resisted chiming in on this one; HOWEVER, I've been a musician for 48 years. I play anything and everything from Bach to Rock, as the saying goes. As far as Rap goes I'm closer to hobie's view than not. Let's just say that Rap is not a genre that appeals to me on any level. That being said, I understand that many people like it for many reasons. Frankly, I've never been a lyric guy. For me its about melody and, especially, what's going on in the background with the other instruments. I think most people who play intruments would feel this way.
No doubt that Rap has made it's place on the music scene just due to its popularity; so I won't discount it. I just prefer other styles.
When it comes to lyrics I'll take Johnny Mercer, Sammy Cahn, Cole Porter, Donald Fagan and Weird Al Yankovik.