I hear that people feel FF IX was the underdog or forgotten a lot, but this has never been true in my experience -- everyone I know that has played the PS1 era Final Fantasy games knows and (rather fondly) remembers IX; 8 seems to be the real underdog with all the hatred leveled at it.

That said, Neptunia does bring up a really good point, and I'm sure that people that missed 9 probably were swept up in PS2 hype. It is also possible that many players picked up the series with FFX, then went back and played VII, since it was the PS1 FF that got the most attention, for a sample and never explored 8 or 9.