Alright, I'll try to properly articulate what I'm trying to say here.

Me and a friend of mine have seriously been thinking about the plot of FFX lately. Here's our conclusion:

Since the Zanarkand that Tidus was born and raised in is a dream, wouldn't that make Jecht a dream too?
If Jecht is a dream, his being Sin is a dream.
Sin is a dream.
They spend the whole game fighting an imaginary product, a dream.

So eh.... wtf? Why base a game on defeating something that doesn't even exist?