Next to FF 10, FF 9 was my favorite. Yes, I do think it is VERY unerrated and unappreciated by many.
I see lots of people who bash at it even, saying it isn't worthy to be part of Final Fantasy.
But I really enjoyed it because it's unpredictable and I liked the environment and story very much.
And also the Is-Kuja-gay-or-not question you have in your head the whole time you're playing it.
Kidding.