The emotional ties that was built between Yuna and Tidus from the beggining of the game until the end when Tidus and Auron were sent was what really pushed me.

For me I think it was the musical score that really nailed it. When I watched the ending without the music, I didn't feel too bad. When I just listen to the theme, "Setuki da ne", I get teary eyed fast.

Watching the ending with the musical score is really eye watering.

During gameplay we hear that theme over and over again and somehow we are conditioned to the fact that this theme song is played only during happier times. It's only during the end that the song is played in it's full glory, but to a sad ending.