6 wasn't especially zany Japanese plot stuff, given that most of the zaniness came from a crazy guy using the super magical statues to do crazy things. No where near the same league as some Gainax anime or most of the later FF games. :p
7 gets absurd. 8 turns absurd towards the end. 9 does the same. 10 sorta does, though not in an especially plot-development-from-left field... I mean, I could see 10's story being produced in the West just fine. 12 was barely Japanese at all which I think they were specifically going for, trying to have a very political-based realistic plot.
Haven't played any of them since 12 so I can't say on that front. The PS1 era plots were definitely ...silly. To each their own. Especially in 8 and 9's cause I just try and ignore it and remember the rest of the game.