Just a few of my favourites -
Richard Pryor - Ground breaking

Bill Hicks- Same

Dara O'Briain- Current and hilarious

Chris Rock- Probably a comedians favorite comedian, controversial but hilarious with it.

Stu Francis- Current one liner king for me, very clever with excellent delivery and timing, here's a sample -

www.youtube.com/watch?v=bV9wsPghPPY&feature=related
(bROKEN aRROW PUA HVI Master, Wed 17 Nov 2010, 11:29, 2 replies)

Bill Hicks
Utter genie arse
(Falco, Wed 17 Nov 2010, 11:36, closed)

Agreed
If people not familiar with him watched him, they may wonder what all the fuss is about but he was one of the first people to do that style of act.....A true great, just ask Denis Leary, he dined out on Bill Hick's comedy for years and they were mates. Hack!!
(bROKEN aRROW PUA HVI Master, Wed 17 Nov 2010, 11:49, closed)

Chris Rock is fucking hilarious, agreed!
I have much love for George Carlin, also, and Robin Williams, I saw Alan Davies once and he was brilliant :)
( SigmaX0 Dear Die Hard. You rock!, Wed 17 Nov 2010, 14:18, closed)

Not a huge fan of
Robin Williams but can't really say I have seen his early stuff. However if it's as funny as he is hairy then it would definately make my top 5. Now George Carlin is probably my favourite from your choice...He makes some great observations like -

People who say they don't care what people think are usually desperate to have people think they don't care what people think.
(bROKEN aRROW PUA HVI Master, Wed 17 Nov 2010, 14:45, closed)

Chris Rock was funnier when he was an angry black man.
Not sure if the success has made him less angry, or being less angry made him more successful. He used to be /very/ political.
( Sextant goes to him is emotionally erect, on this day, Wed 17 Nov 2010, 14:45, closed)

Valid point he has chilled....a bit
and trancended his humour beyond the realms of just black comedy to a wider audience. He's still fairly political though but he does do a lot of relationship stuff.......The commanding voice in bed gag he did is very funny....and true.
(bROKEN aRROW PUA HVI Master, Wed 17 Nov 2010, 15:31, closed)