Since i've not played all of the games I say that I liked Tidus&Yuna though their love wasn't complicated at all (in that matter cuz their feelings were obvious though this love wasn't easy in any part of the game). I liked the elements in it but I guess i'm the only one who liked their love story.
Zidane and Dagger (+ Eiko trying to mess up) stroy was cute but i would have liked some real action between them.
VIII.. Squall was surely feeling deeply for Rinoa but cuz i did not like the game much it killed their romance for me.
And I don't know about Cloud... was there even a real love story in this game?