I understand why Fur Elise, for instance, is popular...it's not 'unreachable' for most amateurs, has a melancholic melody, etc. Flight of the Bumblebee is fast, as is of course full of sixteenth notes, so it is a convenient example of 'virtuosity' (at least for the layperson).
But what of the Fantaisie Impromptu makes it so popular among the mainstream? After I play some piano piece, sooner or later someone in the crowd asks me if I know it.
What about it makes people so interested in it?