May I be the first to offer Stan Freberg?Besides his radio work,his ad work still influences many commercials today.
Oh, I know. That’s exactly why I said it. Groucho said in at least one of his books that they improvised all the time - but it seems fairly well-documented that they didn’t do so in the movies. So I’m just wondering how much improv went into the original stage shows.
Well as **Exapno Mapcase ** said they cut a 1 hour taping to 30 minutes. There is nothing that says just where they cut that 30 minutes out. 
Furthermore if you have ever hung out with professional joke writers, they are quick. I had a co-worker that had dinner once with Harry Anderson and Rinhold Weege (both from Night Court fame) He told me he had to leave the table, he was laughing so hard he tought he was going to pass out.
Those guys are QUICK
I did watch an episode, and I admit they edited things in such a way that they could have cut pauses. And I do know how quick comedians are; I’ve hung out with them and done standup. That said, just from the look of the set, that layout is still hard to envision. It’s also hard to picture the conversation between Groucho and his guests just coming to a standstill that often, it would have been really stilted.
If I can say, I don’t think there can be a best comedian. It all depends on our sense of humor. I love slapstick such as the Stooges, Edgar Kennedy, Laurel and Hardy, Chaplin.
Then there is stand up, then movies. Brooks is a great writer but without the right people how funny would it be? Certainly cut short was Benny Hill, I got to see live in England, he was amazing in writing, stand up and acting, his faces alone were a thousand fold of laughs! Sometimes offensive is funny but if thats the entire act then like the old Eddie Murphy it get old fast!
I think it’s more likely that we just don’t have enough distance.
If we were talking about the greatest comedy genius of the 19th century, we’d have a lot more consensus - I’m guessing Mark Twain would beat out Oscar Wilde and Thomas Nast, and very few other names would come up.
For 18th century, Ben Franklin > Jonathan Swift.
Anyway, when is lack of an answerable question stop people in Cafe Society?
Mark Twain would be the obvious choice, but Lewis Carroll deserves serious consideration. His best stuff (such as the Alice books and “The Hunting of the Snark”) remains very, very funny if you have the right kind of mind, and I can see his influence in a lot of the humor, especially British humor, that has come along since.
For more recent examples, I’d suggest Lenny Bruce and George Carlin, who gave comedy a whole nother dimension.
And Gary Trudeau. Funny and who else could do what he does?
I’m going to toss out a name here that has not been mentioned.
Bob Newhart.
The accountant turned stand up comedian.
His stand up routines are so damn funny he is doing the exact same routine over 40 years later.
You’re whoosing me, right? An accountant?
Nope, not a whoosh
From here:
Newhart an accountant seems like something he would wrote about. 
As the media changes so does the top comedian. Charlie Chaplin, Buster Keaton Harold LLoyd. all were remarkable for their time. But their time disappeared with talkies. So Laurel and Hardy,Marx Bros. and Abbott and Costello, Three stooges came along. Much of what they did on celuloloid were sight gags. On stage and tv Red Skeleton, Milton Berle and others reprised and modified the Borsht Belt and Zigfield follies acts.
Then we had stand up .Alan King, Henny Yougman types.
Then Lenny Bruce came along. Much more cerebral and willing to push the bounds of society . He joked about sex ,politics and religion and used the vernacular.
He paid for pushing the limits but opened doors for Carlin, Murphy, and Pryor. Redd Foxx was doing it but in Harlem , without big notice.
Carlin has been damn funny and thought provoking for many years. Pryor was a comedy genius who saw the opening lenny gave and ran through it.
But nobody rattled cages like Andy Kaufman. He rejected the entire concept of amusing your audience but made tham part of the act. He tried to provoke response and he got it. He broke all the rules and targeted his audience with lazer like precision. Like when he went after professional wrestling and women at the same time. He had them so pissed it was hilarious. I vote anddy. He knew people were toys and had to be played with.
Andy Kaufman wasn’t only unfunny, he didn’t even try to be funny. He was a performance artist, not a comedian, for most of his career. He probably amused the hell out of himself, but that doesn’t take comedic genius.
He was hilarious.
My vote is split between Chuck Jones and Gary Larson.
And are there any female comics (or comediennes) in contention? Gracie Allen? Fanny Brice? Dorothy Parker (does she qualify?)? Lucille Ball? Carol Burnett?
In truth, the person who opened the doors for this kind of humor was Mort Sahl. He became known several years before Bruce and had several hit albums first. You can see a lot of him in early Woody Allen. He was the first comedian to do political humor since Will Rogers and it was a bigger part of his act than Bruce’s. By improvising off newspapers he also allowed other comics the freedom not to have to stick to set routines but do looser sets that mirrored the live rock music scene of the 60s. (Ironically, Woody Allen never improvised and neither did Carlin or Pryor early on. That would take years to change.) Bruce is more influential on a later group of comics who were able to just assume the breakthroughs of the earlier generation and go on from there.
You either love Kaufman or hate him. I agree with Marley23 that Kaufman was a performance artist rather than a comedian. That’s a different list entirely.
Just to play devil’s advocate for a second here, by guiding off Exapno’a post about Woody Allen’s multitude of fields:
Fair enough, but he didn’t actually produce Annie Hall. To the best of my knowledge, the only person who was that good at putting together that many aspects of a comedy is the only one ever nominated for Best Picture, Screenplay, Actor, and Director on the same flick: Warren Beatty.
Which, for a guy who rose to the top of show business as a writer and director and producer and star of dramas, has to be worth some kind of honorable mention, doesn’t it?
(Especially since it’s sandwiched between (a) having another comedy win the highest award from the Writer’s Guild of America back when Woody was still just getting the honor of being nominated – and (b) having yet another comedy still racking up that kind of nomination well over twenty years later, when Woody wasn’t?)
It’s an off-the-wall choice, sure, but name me someone else who could run the table.
Isn’t there a column for “actively loathe?”