At least Zelda's story is self-contained and focus more on the gameplay. Kingdom Hearts on the other hand, has a convoluted storyline that no matter which KH game you start off on that isn't KH1, it's still downright convoluted and confusing.
Face it, Kingdom Hearts can't even do a storyline since it trips up on its own continuity. From a KH-retarded fan point of view, it constitutes depth and deep storyline. From everyone else's point of view, it's convoluted mess that requires you to play every KH game if you want to understand. I can enjoy the storyline and I would have fun with it. Is it a good storyline? fluff no.
Persona has a better storyline
Planescape: Torment has a better storyline.
HECK, Fallout 3 has a better storyline and that's the pinnacle of bad storytelling for a western RPG imo.
Kingdom Hearts does not have one. As you described, it is convoluted and messy storyline.