I don't find any of the genres as a whole to be great or terrible. They all have some good stuff. I grew up listening to dirty south rap and old school Outkast is still as good as it gets. T.I. is very good. So was Ludacris when he forat got started. The Nappy Roots are awesome.
However, the bullshit that southern rap largely became with clowns like Juvenile, Young Jeezy, Lil Wayne... holy fuck, that shit is terrible.