Every region of the US has its era. Right now, the south is dominating the game. The southern style of flow is what's popular right now probably because of Wayne (or Houston, depends how you look at it). Radio stations play nothing but Wayne, *Drake, T.I., Jeezy, Ludacris, etc. And that won't change until they heavyweights either fall off or retire...which I don't see happening for another 5 years at least.
East Coast no doubt had their era, and their style is still quite popular today. People like Jayz, Fab, and Kiss, are still keeping up with the South. But when JayZ retires....If JayZ retires, New York/East Coast will fade.
What happened to West Coast rap? I'll tell you, Pac died. But during his time and even a few years after.
The West was dominant. They are trying to make a comeback. Game is just tryna hold it down long enough for new artists like Nipsey Hustle, Fashawn, and Jay Rock to get it together. Will they ever? Only time will tell.
I think Midwest is next up tho. People like Eminem, and Kanye have been killing the game, laying the foundation for up and coming artists like Big Sean and Freddie Gibbs. The reason I say they are next up is because Eminem and Kanye are still relevant. Em has a few more albums in him and Kanye isn't going anywhere for a while. Yes, southern heavyweights like Jeezy have quite awhile too, but they aren't on the level of Em and Kanye.
Just my thoughts...what are yours?