It's hard to find words. I always enjoyed his work with Carol Burnett on TV and in Mel Brooks' films.
Korman was a perfect straight man, but he could also be very funny in his own right (as you can see in this clip). I remember watching these parodies on The Carol Burnett Show as a kid. I didn't understand all the references at the time (my parents would fill me in a bit), but found them hilarious anyway.