If you're talking listening to the CD: Dave Attell, Chris Rock, Dane Cook, Frank Caliendo, George Lopez, Daniel Tosh are all classic.

I'm meh on David Cross and George Carlin, both solid just not quite me.

Carlos Mencia's DVD is super cluth. That Dave Chapelle you mentioned is superb.

I've been DVRing Comedy Central Presents so if I really thought about it I could probably make a top 50 list (Megan Mooney and Jimmy Carr are the best I've seen recently).

{EDIT: Dave Attell is easily #1. Anyone who picks another comedian hasn't listened to the CD.}