It is always quite risky to use superlatives when talking about a musician and even more dangerous to crown an artist as "the greatest". Because what are the objective criteria that would allow anyone to tag someone else as "the greatest" of any field? Is it even possible to compare a jazz pianist to a classical pianist? I'm not quite sure about that.
The fact is, great classical icons like Toscanini or Horowitz once discovered a tremendous jazz pianist and were absolutely stunned by his virtuoso technique.
Classical piano legend Vladimir Horowitz, who frequently came to hear Art Tatum play, said that if Tatum had taken up classical piano, he'd have been outstanding in the field**. (Other sources quote Horowitz: "If Art Tatum took up classical music seriously, I’d quit my job the next day.")
It is said that Arturo Toscanini once arrived an hour late to a Carnegie Hall concert and told his audience: "I’m sorry. I was down in Harlem listening to Art Tatum and I was fascinated by his music."
Even Rubinstein is quoted as saying: "I am listening to the world’s greatest piano player", while listening to Art Tatum during a performance at Harlem's Onyx Club, a club he very regularly went to.
Does this make him "the best piano player ever" as some people call him? I am tempted to say that it is impossible to determine who "the best piano player ever" is. Even in classical music, this is a difficult thing to do. Is Rubinstein better than Horowitz or Gould or the other way around?
Let's keep it this way: Art Tatum certainly is one of the best jazz pianists in history, all jazz critics and jazz lovers will agree on this. Let me quote Rex Stewart again, because he knew Tatum and wrote an absolutely recommendable portrait of Art Tatum for the Downbeat Magazine back in 1966:
"Genius is an overworked word in this era of thunderous hyperbolic press agentry. Still, when one considers Art Tatum, there is no other proper descriptive adjective for referring to his talents. (...) Perhaps Art Tatum would have been assured a firmer place in musical history if he had not alienated too many of the self-righteous aficionados who preferred their piano sounds less embroidered, less imaginative and more orthodox. Therefore, it follows that Tatum would never be their favourite pianist. Posterity tends to prove that Art requires neither champion nor defense, since the proof of his genius remains intact and unblemishes. The beauty within the framework of his music transcends the opinions of critics, aficionados, fans and musicians themselves. For the truly great, fame is not fleeting, but everlasting."**
But what's your opinion on this? Who would be your personal favourite pianist?