I think it all depends on how you compare them. One piece can only be overplayed in relation to another. It also depends on who performs the piece,,,Moonlight sonata is played by a lot of bad pianists...bhut how often do we actually see it being played by professional pianists? It is a great work when played well...but that is very rarely heard.
I think the problem is...many of the great works of Godowsky, Busoni, Feinberg etc...was that they were writing for themselves, and they and few others could play them. So they were not heard as often, and they didn't have tv's and internet to advertise the music. Plus music was held much higher in society. I mean to go to a concert back then was a big event, and usually for the middle upper classes. Now...the music of these masters is everywhere, and has been opened to a whole new breed of pianists who listen to it to marvel at the speed at virtuosity. It only takes a few minutes of reading the writings of Busoni, Godowsky etc...to realise that that was never what they intended. Godowsky pushed the limits of technique so a whole new world of expression could emerge from the piano.
Have we any living pianist who has the genius of Godowsky, Alkan, Liszt, Rachmaninoff? Now we have many great pianists, but they don't play very often! Look at Zimerman, he doesn't exactly play all the time. I don't argue that Hamelin isn't a great pianist, I have my own opininions on his playing....but I think it is safe to say that his playing hardly burns with Romanticism.
Why is Alkan underplayed? Because he has now got such a reputation for being "raped" by bad pianists, and that it is all about virtuosity. People are not really interested in that at all. They go to a concert to enjoy music.
I think the way forward, is to include these pieces in normal recitals, and stop this whole concept for rare works. Like why not just throw some Alkan into a recital with Mozart or Bach? It would work. Instead of forming recitals of all rare pieces which will just include enthusiastic amateaurs. It would be quite easy, becasue you would get audiences coming to see a Bach Partita...then you have them in the hall....THEN play Alkan Symphony or something, and they may just like it if it is play well.
The problem is not the music, but the appreciation of the music by pianists who are pianists and not musicians. How is it that a non musician can still love a Schubert song, or Beethoven sonata, and then suddenly say erghh to Alkan Symhony? Is the music of a lower quality? Or does one have to be trained to appreciate this music?