* The Biggs scene. It really should be there, adds a bit more to the whole Yavin battle sequence. Not sure why they cut it on the original release, even without the Tatooine Biggs scenes, it could fit there, since Luke had mentioned him ("Biggs was right..."), and it felt like they knew each other.
* The celebrations scenes at ROTJ. The ending of ROTJ always felt kinda empty to me. They destroyed the empire, and they are out celebrating with Ewoks? What happened on the other planets? Also, yub yub was not my favorite song anyway...
* The matte lines cleaning up, obviously. All those artifacts, transparencies (Hoth battle), black boxes, distracting matte lines, projections (Rancor scene), light sabers going off (Obi-Wan spinning his lightsaber, Vader's when the door shuts down on him), they should be fixed.
* The new Jabba palace song replacing that horribly dated Lapt Nek thing. BUT... with the original scene. No CGI added. No Bobba Fett flerting.
* People on Cloud City listening to Lando's announcement, and the new window views. I'm fine with that.
* I would keep Jabba's scene as a cut scene, which you could watch over the extras, with the original actor AND the CGI as alternate angles, but not on the movie itself.
* Ian McDiarmid COULD be on ESB, but mouthing the original words. Not changing the voice, keeping the original audio and having him mouth the words. Could work.
* The CGI sarlacc pit, if remade, COULD work...
That's it. The rest is crap.