>>718376791 (OP)
I'm playing through them (for the first time) now actually, nearing the end of VI.
My take on the 2D games:
V > VI > III > IV > II > I
I'm assuming none of the future games will beat FFV with its insane level of customization, especially moving into the 3D era.
Hated how little choice you had in anything with IV ("You'll play the classes WE want you to play, when WE want you to. And we'll take them away when WE want to."). VI is also strongly story focused, but with Espers and party management there's still a ton of choice.