Anyone care to spoil it for me? (Gonna contain spoilers, guys.)

[Little Blue]

A lot of this is just going to repeat what BG-57 and others have said, but I'll say it anyway as I have other points to add...

Spoliers below...

Why is Auron so freaking... the way he is all the time? Like when Zanarkand was being destroyed, and Auron just stood their calmly saying things like "They called it sin." as the city was crumbling around him. He seems to know the answers to all the mysterious questions about the story, but he never outright says them. He hints onto them, and that's lame. Why doesn't he just come out and say it?!?!

He's already done the pilgrimage before, he knows what's going to happen (in terms of the pilgrimage at least). He's also dead, and a bad ass tough guy by this point in the game. He knows what Sin is so he has no reason to fear it, and if he let out all the secrets early, the story that you love so much would not last very long. He even gives a reason why he never tells anything :"If I told you, would it have stopped you from coming?" (something like that) meaning that it would have been pointless to reveal it earlier.

And is Yevon a bad guy? Everyone worships him, but by this time in the game, I'm questioning that.

No Yevon is not a bad guy, or a good guy, he merely exists to summon. Zanarkand was losing the machina war to Bevelle. In a last hope to preserve his city, he commanded the people to become the Fayth that we see on Gagazet, and he created Sin as an armour to protect him while he summoned Zanarkand from within Sin.

According to Maechen, and other sources, Bevelle discovered the Fayth on Gagazet, and Sin. They assumed Yevon summoned it from those fayth, and to quell his wrath they began glorifying him, hence came about the Yevon church. Yunalesca also played her part in this by giving the Church a purpose to allow the people hope. (A somewhat summarised account)

And was Tidus really from Zanarkand? Was it really destroyed a thousand years before the time of Wakka and all those guys?

No, Tidus is not from the Zanarkand 1000 years ago, before it was destroyed, Tidus is a summoned being from Dream Zanarkand. ie, he is an Aeon just like the rest of Zanarkand, and like all aeons, they have a physical presence in Spira when being Summoned. All Sin did was drag Tidus from where ever Dream Zanarkand is located and dump him in Baaj.

And if Yevon is a bad guy, how did it get all twisted about him being a good guy? And is Jecht really sin? If so, how did he turn from a regular dude into a huge... sin?

Jecht is Sin. He became the fayth of the final aeon for Braka's final summoning. When itdefeated Sin, Yun Yevon possessed Jecht, using him to build a new Sin on.

Also, BG-57, I'm willing to bet that not every final aeon succeeds. If the bond is not strong enough, the aeon would fail. I know people would argue that Yunalesca wouldn't grant a final aeon unless the bond was super uber strong betweent the fayth and the summoner, but she wishes to give people hope, so I believe she would allow them to use the final summoning in case they did defeat Sin. Seymour nd his mom are a perfect example of this, Seymour is 100% unwilling to let this happen before his mom becomes anima, yet Yunalesca stll granted him the power.

And Yunalesca... Why you gotta play a brother like that?

I thought Yunalesca was supposed to be this great nice person, and she tries to ace you! She actually did get me once or twice before I finally got her, but even so.

She believes that only people who have hope should live. When Yuna refused to accept the final summoning, she got a bit mad, and offered to liberate the gang from their sorrow, by death if neccessary, in a similar way to Seymour actually. It seems the only sain unsent summoner is Belgemine...