The manga is okay so long as you think of it as more of an accompaniment to the series. I don't read the manga OR the novels to get a proper retelling of the story, I read them for the extra bits of side-story that get thrown in, or little character quirks that couldn't be added into the game.
Anyway, I don't think I'd really like a KH anime. :/ It usually works okay in the game's 3D, but the stylistic differences between the inhabitants of the different worlds compared to the main characters would just be too weird in animation, I think. Besides, if they DID do an animated series of any sort, I assume it would probably be done by a Disney animation studio? So it wouldn't even be anime, really. (And I'd be disappointed if it weren't animated by Disney because that would just be weird.)
The series is already pretty confusing despite captivating the player for hours on end to tell the story. I think trying to condense it into a movie or TV series of any kind would convolve the story even more and make it hard to get into and grasp.