I too lost interest in Final Fantasy a long time ago, since X. I can't say anything about the MMO FFs cause I haven't played them, but to me, they made the games too linear for me. Now I know most, if not all, FFs are fairly linear, but you used to have an overworld where you could actually go exploring and doing side quests. FF VI - FF IX did this very well. My favorite is a toss up between VI and VII because of the outstanding characters and the excellent stories as well as side quests (fighting the weapons from VII were some of the hardest bosses, especially Emerald). IX was probably my last favorite FF because the gameplay had the perfect balance between the old and the new. It had the more modern feel from VII and the old characters and mechanics from FF I to IV and peaked at VI. After X though, the "feel" of the game changed dramatically, it was still turn-based, but no overworld, only equipping 2 items, one weapon, one armor. XII seemed to go back a bit but the battle system changed. Not saying XII is a bad game, just not my cup of tea. Didn't get into any of the spin-offs either because the original games were fine the way they were.
Square hasn't made a decent Final Fantasy game in a while now, at least for the fans that grew up with IV on up, but perhaps not so for the new generation of gamers. But that's OK, because I still have VI, VII, and IX, and Chrono Trigger, and those are incredibly fun and simple.