Wow, now this is nostalgic. Was just listening to this song and I thought "I already heard this somewhere", then I went looking and: "I found it!".
Remember when I discovered this in a random site somewhere, I would show it to my (child) friends, and we were always like "WOW!". We were impressed by the music, the sync and the animations.
There are definitely a few things I could nitpick, but I can't keep myself from giving it 5, due to nastalgia!