You've missed out on a lot, that's all I can say.
So I hear, I'd probably love them if I played them but I've never seen anything from either that made them looking enticing or even interesting to me. I'd be very willing to try out Kingdom Hearts but Final Fantasy I just wouldn't know where to begin, I kind of view it as those ships have sailed for me, I'm not going to jump off the dock and try and swim after them.