Well, first of all, before you super-anime wannabe fans gear up your typing fingers to verbally assault me, I would like to say that anyone can see X was the worst.
Why, you swirling vortex of ground zero non-matter, is FFX the worst?
Because. First of all, the game was trying to push itself from the PS1 to the PS2, and shock everyone while doing it. While it retains its Final Fantasy charm and ever present through out the game. But what made Final Fantasy VII so popular, because people were shocked totally 3d graphics existed. Relying on simplicity and isometrically free movements to to create a world that was imaginative and powerful. This trend continued until 10. Final Fantasy had already lost its main crew that had worked for Square-Soft on Final Fantasy by the time they merged with Enix.
Softworks is what the head team behind Final Fantasy VII, VIII and IX. 7, 8 and 9 for the dumb people. Square-Enix had dropped them and now with the approach of the PS2, they were forced to shock the crowd with extensive graphics, wonderful cinematics and amazing gameplay. The cinematics had been far too influenced in outside-anime, as with the characters. Final Fantasy 8 was also sort of this way, but the 2-d characters had been unable to push them.
They had begun production early on, inventing a new battle system that had people thinking faster before they had been before, when FF VII and VIII had the simple "enough attacks and you can use a super attack." While 8 increased the learning curve of the game, 9 had stabalized it very well. Final Fantasy 10 can only be compaired to lower level RPG's, the new age-type stuff with complex fighting styles and managing a continus strain of leveling the same magic over and over again. Final Fantasy 11 is an MMO and uses the Final Fantasy 9 battle system, it skips out. Final Fantasy 12, on the other hand, is a pretty OK, but overlooked of a game.
The "sphere" system of Final Fantasy was overly confusing, but the Materia system of FFVII took some getting used to instead of just equipping magic like the Final Fantasys before it. The Sphere system was confusing and tried to be overly real. Yeah, like everyone carrys around a giant stone slab full of magic. But seriously, the Sphere system was rushed, and tried to seem intricate, but failed to mask it.
The plot of Final Fantasy 10 had looked back on all of the games to see the plots of those games. They realized plots were complicated in the 3d generation of FF, and they pushed to create this goal as well. The beginning was totally rushed, one day he is playing sports in a futuristic water ball, then a real water ball who is his father attacks the city, sends Tidus to a nice beach, and he meets tons of friends. Hoopy-de-do. The PS2 looked kind of bad in the beginning, because it was rushed and people didn't have time to make excellent games. D: Anyway, Final Fantasy 10 was in the peak year of the console, although it was fighting the Xbox and Halo 2, FF10 seemed also to graphically unadaptable to the PS2. The surroundings and characters inbattle are blocky, have the white pixle line inbetween textures like most PS2 games, and moved along slowly and aimlessly for a long time until the plot ended.
The Anime aspect of Final Fantasy 10 was too much. With the bad Japanese pop-songs (You know if your friends heard you enjoying that, you would freak out.) stuck in the game, diverting the magestic score that had brought the games to exreme fame, now only had very few orchestrated songs. X-2 only made this worse, by A. adding the characters extreme love intrest, whitch is subtle in every other FF game, prominent, and having the characters actually SING the bad j-pop songs. The anime had soaked it in a time of orange ghey ninjas who wear headbands, and "Superwolf" anime for fans of Underworld. The game had lost its touch, and many people were fired for it, despite the high game sells.
I have yet to play Final Fantasy 12, but it didn't sell so well, I personally belived Final Fantasy 13 would pick up the lost torch.
I have not sat there and ranted my exact opinions, its a matter of the games real quality. Many hardcore fans of FF were disappointed by 10, but anime fans who were blind to the series loved it. Anime has been dropping to all time lows lately, with "orange ghey ninjas who wear headbands." Can you really play every 3d FF game except 10 and 10-2 and then play 10 and 10-2 and tell me they were the best? No. Every series has its dark spot, and 10 was Final Fantasy's.