There was a lot of comedians of that era that were terrific. I think the thing that separates them from later comedians are the years that most of them put in on the radio. On radio, the timing was everything. Also, I think the later comedians rely too much on blatant off color and filthy language. The only ones then that did were on the bar and road house circuit and they were few.
Props to Lou Costello, and you can hit a number of online old-time radio forums and get the best of Abbott and Costello on radio. (Including the 1948 show, "The Baseball Player," which concludes with one of their best versions of "Who's on First.") But as much as I loved A&C, I'm afraid they (and an awful lot of others) were just a little outclassed by:
And...
I have a large collection of vintage radio comedy and love every entry in it, but there was comedy, and then there were Easy Aces (the link is to five classic scripts from this show, written by Goodman Ace) and Fred Allen. And, once upon a time, these two twains did indeed meet: from 1950-52, Fred Allen was the most frequent semi-regular on Tallulah Bankhead's last-gasp-of-classic-radio variety show, The Big Show...and Easy Aces mastermind Goodman Ace was the show's head writer. (Other semi-regulars included Groucho Marx, Ethel Merman, Joan Davis, Jimmy Durante, Danny Thomas, Ginger Rogers, George Jessel, and---believe it...or not---Margaret Truman.)