To me Final Fantasy VIII will always be the best of the series... but I'm a hopeless romantic.
Final Fantasy VII - IX to me were the last of the good Final fantasy games because that was when they were last accessible to a large multitude of people. You didnt have to be a hardcore rpg player to get into Final Fantasy VII and play it through to completion, get caught up in the story, and see it through.
These days, I find RPG's, especially Final Fantasy ones, a bit too over the top and time demanding... not only are they massive time sinks, but the amount of management required in order to pull of their 'active combat' systems are unnecessarily tedious. Final Fantasy X was OK, but it felt like it required more effort to play and I didnt feel as much that I was playing a game as pressing buttons to continue the story. Final Fantasy XII just flat out bored and frustrated me because there were just too many damn things to manage with all the gambits and people running around using up my damn potions every time they got a scratch if i didnt specifically go in and tell them when and how to use them through a gambit. The weapon licenses just added to the tedium. Sometimes you just want to PLAY a game, but Final Fantasy XII felt like WORK, where you had to pour through manuals and get used to using it. It was about as fun as an excel spreadsheet.
Final Fantasy VII was far shallower than games by today's standards but it seems to me that Square Enix is making Final Fantasy games that are more concerned with cinematic badassery than with "FUN"... and thats a problem. When telling a story becomes more of a focus than the player actually ENJOYING the game, you've lost your way.
Maybe I'm just getting old, but it's even the simple things like being able to name my characters whatever the hell I want that I miss. Yes, I'm sure Bwanaperedontis is a bad ass name for a elf knight, but you know, I kinda like the name Charlie, and thats what I'd want to name him if given the choice. But since Final Fantasy seems hell bent on giving me choices I dont want while restricting me from making choices I do want, the series is slowly losing me.
Every few years I go back and play final fantasy VII and VIII to remind myself what it was like to have a Final Fantasy game I enjoy immensely.