Which one do you think is the hardest? Such as finishing the whole story, sidequests, obaining special items and summons and eliminating bosses, etc. ?

I vote the PAL FFX version for having the hardest bosses, it was incredibly hard because I needed to level a lot, obtaining special items, maxing all spheres in order to beat the dark aeons (especially Penance) effectively WITHOUT using the cheap Z aeon. The story was a tad hard, the story bosses such as Sin were kind of hard sometimes too.

Oh, by the way, using resources such as strategies of how to kill bosses, where to get items, etc. doesn't count