Medtner is my favourite 20th century piano composer.
Sadly, it tends not to resonate with audiences as well as it does with pianists!
The lack of 'big tunes', I suspect.
Hopefully, he will one day become a household name in the west
I think that comparing Medtner with Rachmaninoff does neither any favours; yes, they were each Russian and of the same generation, yes, they were each great pianists and composers and yes, each worked within traditional overtly tonal languages and they each had much admiration and respect for one another and dedicated piano concertos to one another, but there the commonalities end. The elder of the two became far better known and more widely appreciated than the younger, partly perhaps because of the "lack of big tunes" (although where are they in late Rachmaninoff?) and partly because Rachmaninoff wrote in many media whereas Medtner wrote mostly piano music, piano concertos, chamber music and songs for voice and piano.
Medtner has been greatly rehabilitated in recent times, with pretty much every one of his works recorded at least once, but to suggest that he was a greater or lesser composer than Rachmaninoff is a
faux pas. Despite the far wider apprecaiton of his work that performance, broadcastas and recordings have enabled, I doubt that Medtner will ever become "fashionable" any more than will Busoni, a fact which, in each case, is in no sense any kind of value judgement. He always had his supporters and devotees, however, one of the earliest in UK being Sorabji.
Best,
Alistair