I love Late Romantic and Neo-Romantic music best of all, and greatly admire Rachmaninoff, Scriabin and Bortkiewicz in particular. I've listened to numerous recordings of Medtner's music, as I'm most eager to like it. I have his sonata scores here as well. If I could totally enjoy some of his music, it would open up new repertoire possibilities for me.
One thing I find that seems characteristic of his compositions though is that he's very stingy with a melody. Reminds me, for example, of that bare fragment of a suggestion of a melody that Brahms used in his first Rhapsody. And like Mendelssohn, he seems to nearly always prefer rapid tempos. Another hallmark seems to be that he writes a lot of filigree material for the right hand as well as the left, such that no matter the actual form of a composition, it tends to sound like an etude. I've heard some of the sonatas and fairy tales, but not the other character pieces--perhaps that's where I'm missing an important dimension of Medtner. Finally, I've also come to believe that Medtner's music is very much an acquired taste. I doubt that anyone would dispute that this music is not as readily accessible as that of Rachmaninoff, Scriabin or Bortkiewicz. Thus, it can be hard to warm up to this music, never mind take an instant liking to it.
I don't make these comments to be at all critical or disparaging. Far from it. Medtner's pieces "have their moments" to be sure. I would agree he has great imagination too. It's just that one has to invest a lot more time into deciphering his idiom through repeated hearings. This may account for the fact that Medtner has never caught on with audiences in a big way--or many pianists for that matter--over the decades to the extent that some of his peer composers have. So for me, appreciating Medtner remains a work in progress.
Mine is probably an uncommon view here in this forum, but that's OK. We're all different in our perceptions.