When west coast gangsta rap started dying out on a mainstream level, east coast rappers capitalized on it and brought their own spin to the genre. 50 Cent was the "icing" on the cake. It's still "gangsta rap" but the substance is gone from it. It's not about the message any more, it's about an image, which is why it's "cool" to be a blood these days.
"They told us west coast gangsta rap was wack, then sold it back to us"-Ras Kass