For me the only artist who successfully bridges that completely dis-associative gap between the underground and mainstream rap in 2008 is Jayceon Taylor b/k/a The Game. Now that's not to be confused with me saying that The Game is a cutting edge lyricist, or that "L.A.X." is even the best album in his catalogue, but this was the hardcore hip-hop artist that wound up in heavy rotation on the radio and video outlets who I thought "It's not overkill. I'm not sick of his songs or tired of his flow." As I went back through the choices for music videos in 2008, The Game featuring Keyshia Cole kept floating to the top of my list each time.
When I say that 2008 is schizophrenic though, you'll notice that side by side with some of the grimiest dirtiest most trap artists from that era are videos from the likes of Charles Hamilton, Akrobatik and Gnarls Barkley. I can't think of a more night and day shift in hip-hop styles than going from Gnarls Barkley to Young Jeezy.