Not funny; just bitterly ironic.
You've obviously missed a fair bit story-wise when you were playing the actual game, and misunderstood a fair bit of the plot. I don't deny that Kingdom Hearts has its problems (you were right when you paid out the clunky Gummi Ship), but would it hurt to just be ABSOLUTELY CERTAIN you know what you're talking about before you make fun of it?
For example, there's a perfectly valid explanation as to why Kairi and Riku weren't actual Heartless. And Sora was not just stopping by at each world in the universe to find his friends, he had to save these worlds from the Heartless using his Keyblade. There wasn't even that many worlds in the universe to stop at; the Heartless destroyed many of them. I could go on, but I think you get the idea.
Graphics were lame, although the super-exaggerated cartoon style fits this sort of satire. Voices: horrible. I'll give you benefit of the doubt since you admitted that the Donald and Goofy voices sucked, but so did the others. Maleficent was annoyingly screechy, for example.
But worst of all was the lack of good humour. Making well-minded teenage to adult characters like Sora and Aladdin ultra-childish just doesn't pass as anything that would make me laugh. There was one or two points where you did actually have a good joke going, e.g "Good thing I watched Jafar's Revenge!", but the bad still outweighs the good. And as I said, it was also apparent throughout the movie that you didn't interpret some of the "retarded" plot elements right.
"Retarded"? I won't argue against your opinion, but remind me: who's the one who made this retarded crap?