Final Fantasy IX is a brilliant game. 'nuff said. Most Final Fantasy old-schoolers agree with this, but as far as I know it's mostly the newer Final Fantasy gamers that don't have that much love for it. The reason is that it goes against the sci-fi atmosphere and setting that Final Fantasy VI, VII and VIII (and also Final Fantasy X I guess) had. Most newer Final Fantasy gamers either started playing Final Fantasy when Final Fantasy VII or Final Fantasy X came out, and so they're not familiar with the original so-called "fantasy" setting the first games had.

At least that's my theory, even though I am a big fan of the game and didn't start playing Final Fantasy until Final Fantasy VII was released.

By the way, Hironobu Sakaguci has also stated that Final Fantasy IX is his all-time favourite of the series.