It's true that the HD-DVD version looks better. (Except perhaps, for the "color correction". The picture looks way too blue.)
However, was a newly mastered print used for the HD-DVD version? If that same print had been used on a DVD version, I don't think the difference would be as striking. If the DVD version used a poor print, then the comparison is not entirely fair.
We need to see a remastered print DVD vs. the same remastered print on HD-DVD or Blu-Ray to truly see if the high definition formats are that much better.
A good example would be Blade Runner. It was just recently released on all formats. I'd love to see a DVD vs. HD-DVD/Blu-Ray comparison.
Also, like David1 said, how well the source material was encoded is also a factor. The older the DVD, the worse the encoding tends to be. When DVDs first became available, the capabilities to encode material wasn't as good as it is today.
