Interesting question.
I haven't played the game. I was extremely interested in 3DGH at first, but somehow (and independently from review scores) I completely lost interest with every new video I saw. I realized that there's something about this specific retro game I don't like. I think games like Half-Minute Hero, Bit Trip Runner, Cave Story and other modern retro style games take a more interesting approach. Maybe I don't do the game justice. I don't know.
Anyway. I tend to agree with all those in this thread who think 3DGH would probably have been rated lower if it was an actual new Zelda game (i.e. in SD for Wii). I have a feeling that many Zelda fans and reviewers would have called the retro graphics/gameplay a narcissistic idea and would have criticized Nintendo for developing a 100% retro Zelda retail game for the current console and not - say - as a fan service handheld game for DSiWare.
