Don’t know about “best”, but Herbie Hancock is definitely one of the best and he is far more than just a fusion artist. His creds as a straight-ahead jazz artist are beyond reproach as his discography clearly demonstrates. Like the recently discussed career of Miles Davis, with whom Herbie made some of the most memorable and important straight-ahead jazz ever recorded, Herbie’s solo career makes it almost impossible to compare recordings from different periods as they can be so different from the other. He is also a very good Classical pianist. As good an example of a genre-neutral player as there is. The playing and creativity is always at the highest level no matter what style he plays; always with his own identifiable and very hip (modern) approach to harmony. And funky as hell!
Personally, I would say that Chick Corea is very much Herbie’s peer as a fusion player. Corea’s Jazz creds, while not quite as impressive as Herbie’s are still very impressive in their own right. Two different players stylistically with each having his own rhythmic touch. To my ears, Herbie has the more obvious roots in the blues with a relentless soulfulness. Corea’s playing, especially on his fusion projects, has always had for me a kind of wide-eyed “perkiness” with a rhythmic feel slightly more on the front side of the beat and brighter tone and chord voicings. Neither is “better”; just different, imo. Still, as far as overall influence in jazz, I think few players on any instruments have been as important as Herbie.
https://m.youtube.com/watch?v=JHvegyDAi7Qhttps://m.youtube.com/playlist?list=PLYe02mm9HjxK1qoMNToWjJD4HUQhLZkUj