Carrot Top, Jimmy Carr and Dane Cook are probably the worst comedians I've ever had the misfortune of knowing of.
I've still yet to hear anyone better than Pryor, Hicks, Carlin and Black.
Carrot Top's pretty bad. Kathy Griffin is just as bad.
I agree about Pryor, Hicks, Carlin and Black. I dunno if you're familiar with them, but there's some good works out there by guys like Jim Gaffigan, Bill Cosby, Rodney Dangerfield, Gilbert Gottfried and Dom Irrera.