After skimming this thread with my eyes...
Black Rob and Shyne are not underground, they were just crap enough not to make it big. They both had record deals with Bad Boy, as well as interest coming from 50 Cent.
Their tunes/sophomore efforts just didn't go down well with the rest at the time. Take UGK; they aren't trying to make a club banger (even if they are, it's not what they rap for).
Jay-Z is the bomb diggy-diggy dang. Did your mother raise you properly?
Gangsta rap = "I smoke cron", "strip you and get banged on", "sittin' on gold Daytons and my rims spinning.
...