Em the best rapper ever...
Early Nas destroys Em's best shit, especially in terms of lyrics. Em comes hard with the rhyming schemes, but early Nas shit has a level of intricacy and creativity that's off the charts. (The only close competitor is GZA, but that man's flow isnt anywhere near Nas' level.) Em's demonstrated more versatility on the mic, I'll give him that, but jesus fuck, his newest shit I can barely listen to it. New Nas, as of late, has been spitting fire.
I think the question was favorite rappers, not best rappers. I agree that Em's work has been basically shit for several years now.