a lot of it has to do with what Dalkaen said about it not being released in the proper timespan. Apparently this was due to the difficulty of the game, which is probably another reason (although FFIV isn't exactly a cakewalk and manages to be somewhat more popular than FFV - but then, that was available in an easier version as well). The fact that the game doesn't take itself seriously might not help either; people expect angst with their Final Fantasy games. And it's also the sort of game that is much better on a replay than it is the first time through - a lot of the plot simply isn't explained at the time players encounter it, so things that are actually very well explained seem random on a first play through.

This is one of my top three games in the series (VI and IX being the other two) so it's pretty distressing that it doesn't receive more attention :<