Well having rikku being yuna's cousin is what lead to the whole HOME part of the story and Cid.

For me which I'm surprised isn't everyone's, is the laugh scene at Luca and that part at the Farplane when Tidus is talking to Yuna and when Yuna replies "Oh, I'm sorry," her mouth doesn't move at all.

To above 500hrs is a hell of a lot for one playthrough. I didn't even have that much for XII which has a ton more sidequests.