Nobody -- not Oscar, not anyone -- can rival the virtuosity and harmonic genius of Art Tatum. But having said that, I find Art’s playing to often veer into exhaust-the-listener excess. Too much genius in a 3 minute tune can be exhausting.
I’ve heard Oscar play live (not in person, but concert footage or talk show appearances). I never heard one bar of canned/practiced notes. He, too, was a harmonic genius, but one more fluid and audience-attuned. One of the great jazz pianists of the 20th century IMO.
My favorite, though, particularly adjusting for era, is Teddy Wilson. Many similiarities between Oscar, Art and Teddy, but TW played the fewest notes to reach the harmonic sweet spot, at least to my ears. He also absolutely excelled at accompanying singers (so many great recordings with Billie Holiday), which is something Art didn’t do as well.
Then again, it’s kind of stupid to compare great pianists like this. Each one is a generational talent, and once they’re gone, there’s not direct replacement.

