I know the technicians ‘round here will crucify me, but yes, the greatest ‘classical piano’ work is/was/and will always be the WTC!
Technicians, please spare me the details; I know it was not written for the piano, per se, but it was the foundation from whence the forte-piano and today’s ‘modern piano’ departed, and the WTC, along with most of Bach’s keyboard masterpieces, sound as if they’d been written not only for the piano but on a piano; now, is that not the mark of true genius, I ask?(Yes, Bach had a huge forehead).
It surprises me that only the ‘Aria’ from the Goldberg Variations has been mentioned thus far, and I can only ascribe this to a technicality:
“Well, he specifically asked about the piano; bla, bla, bla.”
But I ask, is there any music on earth that plays better than Bach’s on the piano?