There are alot of great artists mentioned in the thread but in my very biased opinion no artist has done more to impact the history of jazz as Miles Davis did.
Albums like Birth Of The Cool, Kind Of Blue, E.S.P., Filles de Kilimanjaro, ******* Brew, A Tribute To Jack Johnson, On The Corner, were not just influential, the music from those albums changed jazz and totally expanded its boundaries and pushed jazz on to new directions.
For any artist to change music once is a great achievement.
Miles changed music 3 to four times during his career.
I don't think that can be said of any other artist in the history of jazz.
Jean Luc Ponty