Mainstream "Rap" and "Hip Hop" is pure sh*t. But there are alot of underground hip hop artists who are amazingly talented musicians and lyricists. The Roots for example are all amazing musicians. And i would like any current "pop" singer try to come up with verses that have more depth, skill and intelligence than Mos Def.
R'N'B in it's present form could serve as torture. It is the holy grail of sh*t music.
Rage against the machine are good but they are not really pure rap.
Wikipedia called them an American rock/rapcore...pioneering blend of hard rock and rap which over time would come to be known variously as Rock, Rap Rock or Rap Metal (Both known under Rapcore), Hard Rock, Funk Metal and Alternative Rock or Alternative Metal.
http://en.wikipedia.org/wiki/Rage_against_the_machine
Other rap that is good, not a lot, MC Hammer (only one song and only because of that dance and dress sense). Overall it is s**t.
[EDIT] Mr. T's raps are good, *hums treat your mother right*