Tough call for me. Don't know any of the more modern shows. SNL has launched so many great careers that I think it has to get my vote -- I know the early casts well, but the last 20 years not so much.
I liked Carol Burnett, especially when Tim Conway and Harvey Korman were in sketches together.
A Hall of Fame vote for Your Show of Shows, perhaps the original great ensemble TV sketch comedy. Sid Caesar, Carl Reiner, Imogene Coca and Louie Nye -- amazing trailblazing show.