The repetitive structures used so prolifically in Schubert's music definitely threw my interest off for a while. However upon playing my first Schubert piece (the ever-popular impromptu no. 3 op. 90/D. 899) I became significantly intrigued by the subtle changes within the repetitions, that, in conjunction with some thoughtful inquisitive playing (not saying mine is, necessarily, more some of the recordings I've heard) I really could got a better sense of his style and realized how exquisite he can be. I've since listened with ever increasing interest and appreciation to more of his works for piano, particularly his sonatas. Although, the smaller Moments Musicaux and the Serenade and so forth tickle me something awful as well. His sonata D. 894 has rapidly become one of my favorite pieces, Richter's outrageously superlative rendition has been continually haunting my recent listening.
And I couldn't agree more that had Schubert lived longer, there really is no telling what awesomeness would have poured forth from his pen. Nonetheless, the best of his works. that we do have, display the tempered musical serenity of a rare and curious musical persona, that can be a genuine delight to play.
I feel as though much of his music demands a level of patience (truly a virtue here) that I currently don't possess often enough to really attempt. For instance the gorgeous and terrifying Moderato which opens the D.894 sonata. However, I feel that as time goes on, my Schubert appreciation will correspondingly increase and deepen and hopefully someday I'll have the necessary artistic stamina to make a go of it.
In fact, I think Richter will really say it better than me:
I could list a ridiculous number of moments in this that resonant keenly with me, but a few of my absolute favorites (at least in this first 9 min. [make sure to check out part's II and III of this movement]) would be; 1:24; the segment starting around 3:50; and the part that begins after the chords around 6:38 (particularly the pensive and stolid wandering bass line found there). And too many more to list besides. I could see how someone could be bored by this work at first (admittedly, I was) but I don't see how someone who really listened to it couldn't be struck by at least some of it. And Richter, as most always, just knocks it out of the park.
In summation: although I can't/won't put a numbered ranking on his piano music (top five etc.) I will definitely say he should be taken as a composer of legitimately, musically challenging music, that no pianist should miss exploring.