Eminem, IMO, holds the title of best rapper alive.
There's no doubt that Eminem is talented, when he's at his best he is amazing, but he's been making so much crap in recent years that I just kind of stopped listening. His performance in Forever by Drake is great though, I like it when he does is more "hardcoe" stuff, that's the only word I can think of to describe it, that's what he's good at in my opinion. Still though, Jay-Z beats him for me, I've seen Jay-Z live and it was the third best show I've been to, only beaten by Foo Fighters (Who I've loved for years and probably always will, Dave Grohl was a big part of my childhood and early teens) and AC/DC who are simply legends, that show kicked all kinds of ass.
EDIT: Bedrock...wow, that whole song is based on a horrible pick up line, I don't really like that song. If you search for Todd in the Shadows on youtube he has a review of that song, and lots of other great reviews you should check out on current popmusic.
Oh and, Gudda Gudda? Seriously? He couldn't find a better name than that? Come on.