Also, I'm willing to put some serious money on the fact that grain has been added to ANH, at least. Again, maybe it's from 12 years of doing this stuff every day, but there's a look to post-added grain that I noticed in a bunch of scenes.
There are two truths: 1) The materials exist to make a fully restored OT DVD, scanned already. 2) Lucas does not want the OT to supplant the SE. The images are being deliberately served up to look worse, from the unnecessary sourcing of laserdisc masters when better materials exist, to the non-anamorphic transfer, etc. They're even running a "campaign" on StarWars.com showcasing the differences between the 1977 and 2004 versions of the films, so that fans can see just how much better the 2004's are. It's a curious move to deliberately devalue a product you just released, isn't it?
_Mike