Although I would very much like to barrel forward with my assertion that Final Fantasy XII is the best Final Fantasy ever made, I am obliged to begin with caveats.
I have not played any of the games in the franchise prior to Final Fantasy X, unless you count the Final Fantasy VII spin-off, Dirge of Cerberus—which you should not. This means that I cannot definitively say that XII is the ultimate iteration of the franchise.
Furthermore, I have not played any of the Massive Multiplayer Online (MMO) Final Fantasies. I have three good reasons for this. The first is that my old internet connectivity situation didn’t allow for the extravagance of playing online. The second is that my bank balance didn’t allow for the extravagance of monthly subscription fees. The third is that playing MMOs involve interacting with strangers on the internet for fun. Hard pass.
My last caveat is that people are entitled to have differing opinions and criteria by which they judge the merits of a game.