1. FFIV
2. FFVI
3. FFX
I count count FFTactics though it would be my favorite game if I did. I only really tend to count the Roman numeral Final Fantasies, and I don't even count FFXI.
I have heard that FFVIII does not get enough love, but almost everyone on this board seems to show that they really like it. I am not at all afraid to say that I am one of the people that doesn't like FFVIII. It is not a bad game, in fact, it is most likely one of the better ones. I just did not like the characters. The Final Fantasy series for the most part has been very character oriented, like most Japanese RPGs. If you didn't like Squall, and if you didn't relate with him, then you probably won't like the game. I personally thought that his transformation as a character was bleh, but that is my opinion there.
I never played FFXII or even saw it really. It came out at a time where I wasn't really that concerned or into Final Fantasy. I like the FFTactics team more than the regular Final Fantasy team, so I am curious to see how that game was. I basically heard that the differences between XII and the other games caught people off guard, and that it was widely forgettable in comparison to earlier ones. I would like to defend it, but I really can't now.