I actually enjoyed the heck out of the Thriller album. Some really good stuff on there IMO...
As for rap, unfortunately it is music. Music is not only melody, it's rhythm. Rap lyrics are done to a rhythm instead of a melody and is therefore more of a percussive type of thing. That being said, I hate it. I can appreciate Run DMC's early stuff as well as some of Will Smith's work, but this gangsta crap is nothing but shock radio.