Here's the thing, my TV is 68cm or so. The difference between SD and HD would be miniscule at the most at that size. DVD is roughly the resolution of 16mm film, and HD is roughly the resolution of 35mm film (though depending on the quality, even a 35mm film can have a significantly greater resolution then HD). It's not until you project it onto a much larger screen - or use a much larger TV that you would begin to see noticeable differences. Heck, a lot of older movies are shot on 16mm (even some movies today are) and so there's not going to be any technical increase in resolution of these movies - you may as well just get an up-scaling DVD player.

This is one reason why I predict average people skipping the HD-DVD and Blu-Ray formats, and people with high-end equipment waiting for a format that will work on their equipment. At least with macrovision you can buy "signal stabilizers" so you can use them with your movie projectors.