It has been roughly two years since I finished the game, so my memory is a bit sketchy, but here is how I remember it being written.
Was Tidus real? It depends on how you deem real. He was as real as the aeons. The aeons themselves were physical manfistations of the fayeth. This was made possible by them all sharing in the same dream, harnessing their telepathic power to the point where whatever they dreamed could be made real by their will. Near Zanarkand you find a massive tower of sleeping fayeth, held in a state of self imposed suspended animation ever since Zanarkand was destroyed. They have been dreaming about Zanarkand ever since, and that many sleeping fayeth made it possible for someone from spira to enter into that dream, and vice versa in the same way it was possible to pray to the fayeth and receive an aeon.
This is why the sending never actually affected Tidus or Jecht. Technically they arent dead, and they are as real as the aeons. auron on the otherhand, well you obviously see him avoid any and all contact with anything that may reveal his secret until the end. Even though there are several hints throughout the game as well.
As for your prior comment about people becoming Aeons, well as I remember it, the whole purpose of the sending was that those who do not get sent face the danger of becoming monsters, since it is possible in spira for their spirits to sort of re-incarnate itself according to the persons thoughts. Apparently it is possible for one to visit Yu Yevon (as seymores mother did) and in much the same way a sacrifice becomes the next embodiment of sin, they sacrifice themselves inorder to become a guardian as an aeon. Like I said, I don't doubt I could be wrong here as It's been two years since I played, but that is how I remember it.
Also, FFX is one of my favorite FF's. The last one I really liked, probably because it was the last project sakaguchi handled before he left square. Not that I don't have issues with the game, the voice acting ran hot and cold, and I swear Nomura was throwing a hissy fit about not being made director, and came up with his most whacked out character designs ever just to derail the game. Thats the only way I can explain religous icons wearing slut wear, or even being naked in yunalesca's case. That and Yuna really did look like she stepped out of memoirs of a geishsa, and dont even get me started on riku being jail bait, or LuLu's victory animation, or the fact that half of the leading order of spira subscribes to V-neck outfits that go down to their navals.
Better stop now before I go into a Nomura hate on rant. Again.
I hear ya on that one brother. You should check out the backlog of some of my posts on the Advent Children thread. You wanna see fanboys get hot and bothered, point out any one of the many flaws in Advent (In fact I'm hard pressed to find anything good bout the film) and the fanboys/girls will cry havok and let slip the dogs of war. As I previously stated, I find FFVII to be the poster boy for overrated in this industry. It's not really a horrible game, its perfectly adaquette and at many points, even very good. But to be blunt, I personally have never seen the appeal of Sephiroth as a villain. He burns down a village, kills a corp exec, stabs a church girl in the back and then hides in a hole for the rest of the game. Personally I think the likes of Golbuz, or even Kain from FFIV have more depth then this guy. Yet many people fawn over him and compare him to the likes of Darth Vader. I compare this to the resume of Kefka, or even Emperor Geshtahl who killed celes's mother savagely just to ensure that Terra would grow up to be the weapon he envisioned, and I wonder how can you even think to compare?