Glam Rap isn't so much a genre as it is a label (usually pejoratively) that's thrown at most hip-hop in the Turn of the Millennium. The earliest form of hip-hop that showed shades of this was probably Eric B. & Rakim's Paid In Full album, followed by the works of Big Daddy Kane and eventually Cash Money Records. Glam Rap is arguably a good way for a rapper to be mainstream without losing "street cred". Sure, they talk about the streets, but not necessarily in the same way as in other, more controversial rap genres.