what a tough question! there are soooo many really good comics.
My list:
These are in no particular order. Their ranking depends on the kind of day I’ve had! 
Flypsyde took my first answer, Billy Connolly, hands down. He was on a show with Whoopie Goldberg once on HBO. Whoopie opened with a few jokes and then introduced him. I was lucky enough to catch it on videotape. Must have been the late 80s or early 90s, because I remember Whoopie talking about first lady Barbara Bush surveying either hurricane or earthquake damage somewhere. ANYHOW…his routine in that stand-up special was the FUNNIEST I’ve ever seen. Unfortunately, I no longer have the video and have NO clue where it disappeared to. So my plea to you people is that if you have this on VHS somewhere, PLEASE let me know. I’m willing to pay for a blank tape, postage, and any time you use to copy it for me!!!
Runners up? Hmmm…
Bob Nelson’s “Football Routine” in the mid 80s was hilarious. Anyone else remember this?
Eddie Murphy in his Delirious and Raw shows, as mentioned before.
And as far as the Mitch guy on Comedy Central…is that the one who was talking about his girlfriend moving in with him, and she was so strict that he came home one day and she had the cockroaches running the sweeper? If so, he was absolutely hilarious. My sister was able to catch part of that on tape, if she hasn’t recorded over it…
Suprised I haven’t seen more mentions of Hicks around here. I’ll second that nomination.
I have to go with these comedians, no particular order since they all have different styles of delivery.
Dennis Leary
Redd Foxx (this man was DIRTY)
Richard Pryor
Sam Kinison
Which means I get to second Lenny Bruce.
(Thank you, Masked Man.)
Bob Newhart, The Smothers Brothers (do groups count?), Geroge Carlin, Jack Benny, Fred Allen, George Burns…
but the best of them all is Bill Cosby. Back in the early '80’s he did a film called “Bill Cosby: Himself”. Just Bill, a microphone and a chair. I’ve seen the video at least 6 times, and each time I end up rolling on the floor, breathless from laughter and praying I don’t pee my pants.
Dennis Miller
Denis Leary
Robin Williams
Steve Martin
Eddie Izzard
This is an easy pick for me: Sam Kinison’s appearance on the Rodney Dangerfield Young Comedians show on HBO around 1987. Several of the performers went on to bigger things (I think Tim Allen also appeared), but Kinison’s solution to world hunger was my highlight.
IMHO, The Amazing Johnathan had one great performance on Comedy Central. However, I haven’t seen anything from him since…
I think the best ones were the ones who could improvise and leave you cackling helplessly when the rules get changed on them and they have no access to a script.
Yet another nomination for Bill Cosby in his prime.
Groucho Marx also deserves serious nomination here.
Also known as his entire dang act.
Except for Driving Instructor.
Which kicks ass.
For me, Sam Kinison. Three out of four albums still make me laugh after nearly 10 years.
“I knew right then that Jesus had never been married. No woman just lets you take off for three days and when you get back you tell her, ‘Honey, I was dead.’ That always works.”
I’ve always kind of felt bad that I don’t get Bill Hicks at all.
-Myron
I can’t believe no one mentioned the unknown comic.
Well, considering I’m from the South, I readily nominate Jeff Foxworthy. He’s much funnier in person than on television.
I also think Sinbad (in standup) is hilarious. Not that funny on the tube.
Let me also put my vote in for George Carlin, King of Hilarity. Anybody remember the album FM/AM?
I love Bill Cosby, too. Hell, he’s still funny!
Oh and let’s not forget Jack Benny. Timing is everything.
Mine. 
I really like Dana Carvey, although I’ve only seen one of his shows. Makes me laugh every time. My friends and I recite it during boring moments in class.
She bought some broccoli
She brought it home
Now she’s chopping broccoli
Jerry Seinfeld. Makes ya’ wonder how he got a TV show.
Though I do agree with Kinison, Williams, and Wright. Redd Foxx was pretty damn funny too.
Post #5
My 2 cents, in order:
Gracie Allen
Jack Benny
Bill Cosby
Gallagher
Rita Rudner
Red Skelton
Johnny Carson
Elayne Boosler (Is she still working?)
George Carlin
My favorites: Steve Sweend and Louis Black.
Parts of Raw and Delirious were funny but I think they’re far from Eddy Murphy’s best work.
For some reason I can’t edit my post, but the first name in my previous post was supposed to read ‘Steve Sweeny.’
My Favorite Five, in no particular order: Dennis Leary, Dennis Miller, George Carlin, Jeff Foxworthy, and Steve Martin.