FF8 is the choice.
FFX-2 and FF12 are tied but way behind. FFX-2 continues the story of Yuna and if you disliked the ending to FFX, you may find the "happy" ending in this one more favourable. But if you liked the ending in FFX, don't play this game. FF12 is not a bad game, but the game fails at what makes the FF series great (really great): having memorable characters that you really care about.
The only interesting character is Balthier but you don't really care about the fate of him or any other character. Battle system is flawed, but play for longer than 2 hours before making the final call (I still disliked it, but it was way better than my initial impression).
FFXI is online.
Basically, walk into FF8 with no expectations and you'll walk out of it very satisfied. It's the only FF that I've managed to clock the full 99:99:99 time for, that's partly because I was young back then and lacked the mad skills, but mostly because triple triad is an addictive game and collecting the ultimate weapons for each character was also fun (and involved triple triad for some).







