(For the record, I love the original versions of the films, however, I have no problem with updating them as long as the theatrical versions remain intact and available, and I suspect that this is the general concensus here as well.)
A NEW HOPE
-Insert a faint Imperial March into the 'music-free slot' when Vader looks around the Blockade Runner.
-Clean-up or re-dub both Vader's breathing and dialogue to match the other movies. This really, really bugs me, and is sure to bug me even more when RotS comes out and Vader sounds as clear as ever.
-Digitally add the tombstones (from AotC) into the Lars Homestead.
-The activation & color of Luke's lightsaber in Ben's House need to be fixed.
-Insert The Imperial March into first shot of Death Star.
-Insert The Imperial March into shot of Death Star after the burning homestead scene, and have it continue on into the interrogation scene.
-Insert a Dug (Sebulba?) into the Cantina; either in the lizardman/wolfman slot or the elephantman/wolfman slot.
-Change arm in Cantina so it has no blood. And make it a hoof to match what we see in the longshots.
-Show Ben's saber tuning on & off; no more of these off-screen sound effects!
-HAN SHOOTS FIRST!
-Insert The Imperial March into the shot of the Death Star after the Cantina.
-Change Jabba's voice & appearence to match TPM & RotJ.
-Insert The Imperial March into the shot of the Death Star over Alderaan.
-Following that shot, insert a scene with Bail Organa talking to another Rebel Leader via hologram (Ackbar?), possibly about Leia's dissapearance and the Death Star. Then cut to Tarkin lookiing at Alderaan on the viewscreen.
-Insert a shot of the Death Star blocking out the sun on Alderaan, with Bail Organa and other looking up in horror. Then cut to the activation of the superweapon.
-Fix the activation, deactivation, and color of Luke's saber on the Falcon. It's freakin' WHITE!
-Change the seeker ball to CG (like in AotC).
-In the scene where the dude comes in and says the Rebels are on Dantooine, change the timing of Vader's line to match his gesture.
-MAYBE insert a scene where Vader reports to the Emperor after detecting Obi-Wan. It makes perfect sense that he would contact Palpatine after storming off ("I sense something, a presence I've not felt since..."). Then have Palpatine tell Vader to be wary and inform Tarkin (He is here...).
-Insert a faint Imperial March when Vader is walking through the Death Star halls.
-Make the Diaogna look more realistic.
-Re-dub all the Stormtrooper lines with Temura Morrrison. This goes for the whole trilogy, including Boba.
-Improve the Vader/Kenobi duel. Some dramatic music (possibly the same from their SW3 duel?) would be nice. Also, fix saber effects (both optical and audio) so they match the other films. The saber effetcs are really bad, and the sounds of this duel are WAY different from the others.
-Change the gunport sequence; possibly more TIEs or have the Falcon be moving (I always thought this sequence was boring).
-Show the Falcon going to hyperspace before Vader says, "They've just made the jump into hyperspace."
-Change Death Star plans in Rebel Breifing to match the ones in AotC.
-Update the graphics on the Death Star.
-Change a couple of the explosions on the Death Star; some of them still look not-so-good. (Other than that I think the space battle looks great. It's amazing how good CGI can be when time and effort is put into it.)
-Insert a scene where Vader goes to Coruscant to report to Palpatine, like Dooku does in AotC. This would take place between Luke's landing the awards ceremony. On a landing pad at the Imperial Palace, the Sith Lords would discuss the death of Obi-Wan, the destruction of the Death Star, and the rise of a new enemy, Luke Skywalker. The ESB conversation would have be altered to go along with this one.
THE EMPIRE STRIKES BACK
-Fix the Taun-Taun effects. Some are good, but others need improvement.
-After Luke cuts the Wampa's arm off, there's a lightsaber deactivation noise, but Luke's saber stays on; have it turn off.
-Add a few more AT-STs to the Battle of Hoth (to sort of establish them for RotJ).
-MAYBE add more Snowtrooper/Rebel soldier fighting into the Battle of Hoth.
-Add a few more background monsters to Dagobah; "Massive lifeforms readings...".
-Change Luke's line back to "You're lucky you don't taste very good."
-In the scene where you see Vader's head, make it so he's watching a hologram of Padme. Audio would be the best way to do this, since you can't really see into Vader's chamber. I'm hoping she sends him a goodbye letter of sorts in RotS, and this could be used here and in RotJ.
-Change the Emperor to Ian McDiarmid. Change the music to Sith Chants/Emperor's Theme. Change the dialogue if to fit with a new ANH scene.
-Again. re-dub all the Stormtrooper and Boba Fett lines with Temura Morrison.
-Update ALL the windows on Cloud City. The SE is inconsistent; in one shot a window is updated, but in another, it's not.
-Add more training on Dagobah, IF IT WILL FIT. Jumping, lightsaber skills, etc.
-Take out the Emperor's scream as Luke falls. Very funny Ben Burt, now let's change it back please.
-Have the Falcon fight some TIEs as it escapes Cloud City ("What about those fighters?").
-Change Vader's line back to "Bring my shuttle", and take out all the new SE stuff. It's totally useless and interrupts the flow Luke's rescue.
-Flip the reverse frames when Vader & Piett talk about capturing the Falcon back to normal. I have no idea why they did this, but the Imperial uniforms make it obvious.
RETURN OF THE JEDI
-Add some PT aliens to Jabba's Palace.
-Do something about the dance number in Jabba's Palace. The CG really sticks out, so either re-do it or change it back to the original.
-Change some of Boush's lines so "Yoto" doesn't mean everything.
-Take out the *BURP* of the big frog. It can still eat the lizard though.
-The compositing of the Rancor is HORRIBLE! The creature itself looks okay, but when it interacts with Luke, it needs a big upgrade. Don't totally replace it with CG though, just fix the compositing.
-MAYBE extend the Boba/Luke confrontation (with a couple of stunt doubles).
-Add some limbs flying around or something as Luke uses his lightsaber on the Sail Barge; Make it look like he's using a LIGHTSABER, not a stick.
-Insert SOME shot of Han flying the Falcon; during the conversation as they leave Tatooine would do. It's a great injustice we never got to see him flying his baby in the conclusion of the trilogy.
-The Emperor's theme is good, but alter it to incorporate vocals (like in the PT, which sounds even cooler).
-Extend the Luke/Ben conversation, with cut dialogue and all (the parts that fit in with RotS).
-Fix some of the Speeder Bike effects. Most are good, but some still need improvement.
-Insert a scene where Vader is watching the same Padme hologram from MY ESB either right before or right after he tells the Emperor about Luke being on Endor.
-Have 3p0 explain WHY the Ewoks join the Alliance; they're being used for slave labor and loosing their home, e