Okay, I used to put a lot of thought into this but not anymore. I figure I'll just throw out some key points and see what you think.

So, I think some of the Final Fantasy games may be connected and may have even been on the same planet.

In Final Fantasy IX we learn that like, everyone's memories is connected and whatnot. That explains why when Zidane was in a shop earlier in the game (uhh I think maybe Alexandria) he says something about remembering a spiky haired guy who carried a sword similar to the one he was looking at (a reference to Cloud). This can be possible because since all memories and whatnot are connected, Zidane "remembers" Cloud. This suggests that FFIX takes place after FFVII.

Also, in FFX and X-2, in the center of Luca where the sphere break tournament begins, there is a sort of monument that looks exactly like the sword atop Alexandria castle. This suggests FFX takes place after FFIX.

Some world maps are similar in the structure of their continents.

Maybe in several of the games where "ancient" civilizations are referred to, they're all the same civilization, but the facts have been twisted through time.

I definitely had some more evidence several years ago but lost interest. Does anybody see any other connections?