The TV version of "You Can't Take it With You" (the Jason Robards version mentioned above) is superior to the movie. THe movie dropped some characters and added a few serious scenes not in the original.

Also by the same authors is "The Man Who Came to Dinner", the movie is great but there's also a TV version on DVD with Nathan Lane that beats the movie version by a mile.

My all-time favorite comedy, if I had to choose one, would be "Harvey" with James Stewart. It's probably the gentlest, most satisfying movie I've ever seen.