The Best Piano Works of the 20th Century

Trilogy, Karn Evil 9-2nd Impression - Keith Emerson
Gymnopedie - Eric Satie
Ecologue for Piano and Strings - Gerald Finzi

I was going to nominate Modest Mussorgsky’s "Pictures At An Exhibition", but during a little research learned that though the work became very popular and often performed after orchestrations were written for it in the early 1900’s, most famously by Maurice Ravel in 1922, Mussorgsky’s original piano transcription was written in 1874, and published in 1886, five years after the composer’s death. I love the work, both as performed on solo piano, and with full orchestration.

The works of Conlon Nancarro for player piano! I have a multi - CD set of these!

Epic piano concertos of the 20th century in my book:

• Rach-3
• Rach- Rhapsody on a theme by Paganini
• Prokofiev-3Ravel- Concerto in G major
• Poulenc—concerto for two pianos
• Bartok- 2 (for modernist listeners)                                     and why not,
• Messiaen: Vingt regards

I don't know about being the greatest anything, but Stravinsky wrote some good stuff for solo piano.  I really like this record and recommend it to anyone who is remotely interested in solo piano stuff. 

https://www.ebay.com/itm/Marie-Francoise-Bucquet-STRAVINSKY-Solo-Piano-Works-Philips-6500-385-SEALED...