Piano Forum

Disclaimer: I am not really very familiar with the Gershwin or the Astrinidis.

Double disclaimer: This is my own opinion.

Triple disclaimer: If you keep this up sooner or later someone's going to accuse you of being a troll. I'm not going to do that, but there a few on this site who seem to have made it their life's mission to strain out trolls everywhere (and in the process scare off most newcomers).

That said, here's my opinion, from easiest to hardest.

Rachmaninoff Op. 3 No. 2. Really. Not that bad.
Gershwin Preludes No. 1 and 3 (not very familiar with them, but a friend played them when he was at a lower level so they can't be too bad).
Chopin Fantasie Impromptu (A-B-A section means the sheer number of notes is kept to a minimum, even though the A section is rather difficult, considering the cross-rhythm and running right hand).
Rachmaninoff Prelude Op. 32 No. 5 (Doesn't sound too hard, but quintuplet- rhythm makes it all very hard to swallow).
Chopin Revolutionary Etude (LH is very hard to get right, and can be very taxing to play fast even when learned).
Rachmaninoff Moment Musical No. 4 (LH is notoriously difficult, even more so than the Chopin Etude).
Chopin Heroic Polonaise (A very mature and long piece. Perhaps there aren't as many notes as in some of the lower pieces, but tying it all together into a coherent story is very hard and some passages are very taxing. Also, playing it without making it too bangy is takes a lot of control).
Astrinidis Prelude No. 2 (Just judging by the sheet music there's a frick ton of notes there to play at a fast tempo!).
Liszt La Campanella (Insane mile-long jumps throughout the piece).
Rachmaninoff Prelude Op. 32 No. 13 (Very long, very mature, very difficult and so many notes even in the slow sections that I just wilt every time I look at it, even though I love the piece. IMO the most difficult piece on this list).

Note: This is my subjective opinion. Perhaps La Campanella isn't as hard as all that. Of these, I have played Rachmaninoff Op. 3 No. 2, Chopin Revolutionary Etude, parts of Moment Musical 4, La Campanella, and the Heroic Polonaise.