I've posted this several times already, but it is always worth retyping, although I could jst copy and paste.

There are a lot of personal reminicies of Liszt worth reading, and this comes from Arthur Friedheim:
"Liszt's technique has been the subject of much discussion and conjecture on the part of those who never heard him. Was it so prodigious, and has it been equalled since? The answer is that it was truly prodigious but that in certain respects it has not only been equalled since, but also surpassed. Moriz Rosenthal and L. Godowsky went beyond Liszt in specialized phases of
mechanisme. However, while Godowsky's chief
metier was dexterity of fingers and Rosenthal concentrated on brilliance and power, Liszt shone in every department of technique and probably never has been approached as a builder of "orchestral" climaxes, overwhelming masses of sound and exciting effects."
Later Friedheim writes,
:..except for more counterpoint and more complexity in writing, the piano music of today demands nothing that was not known to Liszt in his ripest achievements. I could go even further and hazard the logical opinion that Liszt would have developed in our time as he did in his own, and perhaps even shown us things altogether new in ideas and execution."
I agree with this, I think all the piano music that represented an "advance" in terms of demands of technique or sound production, were an "advance" from what Liszt had established, that is, basically everything. Godowsky, Busoni, Bartok, Debussy, Ravel, Scriabin, these people were building off Liszt's achievements, so I don't doubt that Liszt could have mastered their music as well. But it certainly makes for fun speculation!
Walter Ramsey