So I've just been looking around the internet for the best quality version of the *Theatrical* release of Star Wars and found the best official copy available is the 2006 bonus DVD, but the quality is rather poor, even for a DVD.
But then I found this. "Harmy's STAR WARS Despecialized Edition HD".
Basically what these dedicated fans have done (as this is not an official release by any means) is take the video from seven different sources and painstakingly shot-by-shot piece together the highest quality possible video that mimics the theatrical release the closest, in terms of the original SFX, the original soundtrack and other things like colour balance, getting rid of George Lucas' meddling changes that have been introduced much to the disappointment of fans.
So what we have is basically a very good quality reproduction of the original theatrical release, which if you're a Star Wars fan will be very happy to hear about.
Links and info in 1st post.