Good job doubleofive with all the comparison caps.
It is the '97 SE opening crawl that introduced the faster receding logo not the '81 crawl, the '97 and '04 is exactly the same opening crawl as far as I can see. I don't see any tweaking done between them.
doubleofive, you haven't listed the '81 opening starfield difference, remember that the whole opening is unique to that version. Also the different '97 A long time ago... text is different from the '04 version.
The clouds were added to the binary sunset in '04 not '97 and the landscape in the close-up of the suns were removed in '04.
EDIT: you could maybe list the '97 binary sunset as altered also, but I think that is just a colortiming difference, so if you include that, the list will grow considerable. You have a pic of the '97 sunset if you follow the link or should I say moonset. ;)
http://originaltrilogy.com/forum/topic.cfm/Star-Wars-Colortiming-Cinematography-was-What-changes-was-done-to-STAR-WARS-in-93/topic/9805/