I'm talking sales, you jokers. It's widely known that VII is the best selling FF to date... and I'm still waiting for my copy of XIII to arrive so I can even judge it...
Ah, and while we're at it, IX was the worst on PS1. VII > VIII >>> IX
My impression is that you started playing Final Fantasy games with VII, or that you're one of those who judge a book by its cover (i.e. the super-deformed look of the characters.).
IX was to most long time fans of the series a much wanted return to source. Unlike its 2 predecessors, it didn't try to take itself more seriously than Christian Bale on Terminator's shooting sessions. It didn't try to shove our throat with pre-pubescent pseudo-oedipians shenanigans. And more importantly IX didn't have any plot-holes or ambiguous story-telling.
IX was an homage to the series, a gift to the fans of the classics (I through VI), and was remarkably designed and conceived.