He was the comic of New York for most of the 90's. He was the man. If such a title could be bestowed, which it isn't I guess. But still ask comics who were there.
Imo the 3 most imitated comedians are Dave Attell, Todd Barry and Mitch Hedberg. You can go to any open mic comedy night and see at least a few people copying their style.
I used to do 2 comedy mics in the village one at 7pm and then one at 9-11pm in the Village in NYC and then we'd go to The Comedy Cellar right around the corner. We knew the manager and he knew me and my friend and knew we were comics so he'd wave the $15 entrance fee and just tell us to buy a drink or 2 or some chicken wings to support the club which was cool and fair. You had the best of the best comics there at The Cellar and you still do but there's a lot of new comics now and it's a little different. Anyway we'd go there after our shows a few times a month for a few years and Dave would either go on last or second to last. Every comic was great but Dave was on a different level like a notch or 2 or 3 above the best ones. Artie Lange said it and I agree that he's maybe the best club comic in the world or ever. Let's say top 5.