I think you named them all. There's the original three--35mm stereo, 70mm 6-track, 35mm mono; and for later home release there's the '85 stereo, similar to the original, and the '93, similar to the 70mm. Then the '97 5.1, which has its own unique flavour but contains similarities to all three originals in various places. Then there's the one we don't talk about, the '04 abomination, which sounds absolutely nothing like what Star Wars is supposed to sound like in any way.
The '06 GOUT dvd contains the '93 soundtrack.
Empire and Jedi had 35mm stereo and 70mm six-track versions. I don't think they were ever remixed in '85, or if they were, there are no substantial differences to be heard. They were both remixed in '93, and of course '97 and '04. Unlike the first movie, their '04 dvd versions still sound mostly good. The '93 version of Empire resembles the 35mm in content, but has greater dynamics (although one sound effect is missing). Empire's GOUT audio is compromised in dynamic range compared to the laserdisc--I suspect it may have come from a vhs master (either that or it happened during the AC3 encoding). The special edition changes are supposedly true to its 70mm version, but since there are no recordings of it, it can't be stated as fact. I don't think Jedi ever had any differences in content originally.
It's hard to pick out one version as being the best, but I've become most accustomed to the '93 laserdisc track. My pet project was to combine it with the special edition LFE to give it even more power and resemblance to the 70mm mix (or at least how I imagine that probably would have sounded). While I was at it I also patched in the cell bay shootout from the '77 stereo, to eliminate the breaking glass sounds that were added in, and put the Falcon's 'hyperdrive deceleration' sound from the mono mix as a matrixed rear channel effect. It sounds extremely awesome.
I've given some thought to trying to eliminate all of the other '93 additions to try to recreate the 70mm version as closely as possible, but I'm not sure if that will work, or is entirely worth it. Hmm . . .
(Okay, enough plugging my own work. lol)