I read somewhere that Beethoven and Hummel engaged in frequent cutting contests (one on one competition). I would imagine these involved improvisation. I guess I would have to agree with a few other people and say Liszt as the best of all time, but I really have little to base that on. I agree with the previous poster as well, Art Tatum was certainly one of the best improvisors ever, speaking of either classical or jazz.
This is our concern, Dude,
Bri