Wu-Tang Clan ain't nothin' to fuck with.
I use to be one of those people that would say "Rap is crap, dur dur dur," but then I realized I wasn't listening well enough to pass judgement, and I was just being a music brat. Groups and/or individuals like the Fugees, Talib Kweli, Wu-Tang, Dr. Dre, Mos Def, Public Enemy, and The Roots (more so Black Thought) really sparked my interest. I listen to a lot more than that, but those are mostly my favorites.
Mainstream rap is just like any other mainstream genre. It adheres to the formula that sells the most records. The "bang bang slap a ho gangsta" stuff that is on the radio is what sells, so of course it is the type of hip-hop that is pushed.
Hip-hop gets a lot of respect, just not here because most of us are probably white, angsty nerds who listen to awful techno, industrial metal or stuff like Snow Patrol, or maybe live in a country lacking the base of hip hop that the US enjoys.
I always find it funny that people are more than willing to bash "black" music, when "black" music has been the foundation of everything we listen to, aside from Polka. Hip hop was the first music to use samples and looping beats, which turned into techno and other technology based music. Without old blues and field songs, we wouldn't have rock, jazz, punk, ska, metal, alternative, techno, avant garde blah blah blah. The list goes on. Music has a long and complicated history and it's all connected. Everything is worth giving a listen... well, everything not on your local top ten radio station.
Edit - If you have time, here's an hour long documentary about hip-hop. It's pretty interesting. I won't go into too much, but there are a lot of insightful interviews: HipHop: Beyond Beats & Rhymes.