Now, for those of you who haven't beaten [or played] FFX, this might contain major spoilers. Well, you know how FF7 has a lot of mythology in it? If not, read these:

Well, I have another theory [although it may not be true] on the mythology behind FFX.

I belive the real world setting may have been sometime from the fall of the Romans, all the way up to probably the Renaissance. Zanarkand, one of the great machina cities. Zanarkand represents Rome, and the Roman Empire. Sin, represents everything that led to the downfall of the Romans. As you know, it was Sin that attacked Zanarkand, and destroyed the machina cities. Now, when Tidus wakes up 1000 years later, he finds himself in Spira, or in my case, the Middle Ages. Yevon, is the "religion" of Spiras people. In the Middle Ages, Europe [Spira] was Catholic. In the Middle Ages, the Church forbid and Greek or Roman influences, or else, you were considered a heretic [not a follower of a certain religion]. Yevon, outlawed the use of machina, which was used by Zanarkand and other great machina cities. The Al Bhed, are desert people. They are related to the Muslims. During the Crusades, the Christains were trying to reclaim the Holy Lands [Jeruselum] from the Muslims. The "Holy Lands", in FFX, is the Al Bhed "HOME". During one crusade, the chrisitians went in and killed every single Muslim in the city. That is what the Guado tryed to do in FFX. Of course, like the Catholic Church, Yevon was corrupt. Yuna and her guardians, I think represent the followers of Luther, the first group to break away from the Cathlolic church.

In short:

Zanarkand - Rome
Sin -Everything that led to Rome's downfall
Yevon- Catholic Church
Yuna and guardians - Followers of Luther
Machina - Greek/Roman culture
Al Bhed - Muslims
HOME - The Holy Lands
When HOME was destroyed - The Crusades
Spira - Europe in the Middle Ages

This may not be 100% true, but, it was worth a shot, for more reading, check these links out: