Best Comedian Ever? Can you decide?

Still reeling over Robin Williams' suicide. Wow! However, we have a big disagreement going around our house. I did post it on Facebook and the answers have varied so much, showing the diversity and tastes of my friends and colleagues.

Who is the best comedian of all times? It has narrowed down to two choices; Robin Williams or George Carlin?

The discussion started over dinner at Olive Garden last night and continued into the wee hours of the morning. We have been to tons of comedy shows in Chicago and Vegas, so it's really hard to pinpoint. I look back over the years, starting with Henny Youngman, Jack Benny, Red Skelton, Carol Burnett, Tim Conway and the list goes on and on.

Who would you choose, or can you?