The Best Piano Works of the 20th Century

Hyperion released an extensive 'The Romantic Piano' series. Much of it is 20th Century. The Godowski 'The Complete Studies on Chopin's Etudes' 
is worth having. As far as the best, one can't ignore the Shostakovich  Piano Quintet.

Glen Gould playing "Goldberg Variations" by Bach.

@fixedincome---I too love the GV, but that is hardly a 20th Century piano work!