And it ain't like the Star Wars/Jaws fueled emphasis on special effects driven movies with huge budgets has had an unequivocably positive effect on American cinema.  

Speaking from my own memories, what I found different about Star Wars and Empire when they came out was that they were the first science fiction movies (other than Kubrick's totally different in every other way 2001) to successfully recreate some of the feelings I experienced when reading SF on the big screen. Older SF movies just never looked right to me, with their sleek, shiny rocket ships and their unconvincing aliens.

On tv, Star Trek and the Twilight Zone (and probably the Outer Limits, but we never saw that show at the time or in repeats on our channels) produced well-written, first-rate SF, but they never had the production values of the big colour movies and also pretty much stuck to the short story form. But Star Wars felt like a big space opera novel - I sometimes think of it as something like Dune as written by Edgar Rice Burroughs - and that was incredibly exciting to me.

As for the individual films, yeah, the acting is pretty much beside the point, just as it is for Buster Crabbe's Flash Gordon: what you want is someone who looks and feels right for the part and Hammill and Fisher are perfectly fine from that perspective - in contrast to the guy who played Anakin Skywalker in the prequels, who I think was a better actor than the young Mark Hammill, but totally unconvincing and miscast in the (admittedly badly written) role.

I go along with the consensus that the first two are the best by far, with Empire the best directed and best-looking of the films but suffering not really working as an individual film of its own: it feels more like an important chapter in the middle of a big novel than a novel in the middle of a larger series.

Return and the prequels are all deeply, even fatally, flawed by commercial, marketing-driven decision-making, poor writing and, in some cases, casting, but still contain many stunning visual sequences that make them all worth watching for any SF fan.

I saw 2001 before I had ever seen or heard of Star Wars...and still thought it was a great movie. I don't think there's really a correlation between being introduced to "Hard" sci-fi first and not liking Star Wars.

The story goes, he screened it for Spielberg, Millius, and maybe DePalma and a few others, with no effects shots, with dogfight footage from WW2 movies for the third act, and without the music and Millius was making fun of it and Spielberg expressed confusion, but figured George would make it work.  Marcia Lucas helped George focus on fixing things in the editing, to speed it up and mix the effects footage, when it came in.  She pushed heavily for reinserting scenes, like the good luck kiss, to humanize the characters.  Thos around the Lucases felt that it was her feedback and editing that saved the film and refined it to what was seen.  Her influence was also there in Empire, though George butted heads with Kirschner over the time he was taking on scenes, to get the emotional depth.  By Jedi, they had adopted their daughter and Marcia was spending time at home and was not involved with Jedi; but, also, their marriage fell apart, as Marcia had an affair, while George was deeply immersed in his company.

Millius has talked about how talented Marcia was, as an editor and the eye she had for film and talked about how she was frozen out of the film community, after the divorce, to stay cool with George (although the divorce was relatively amicable, by accounts).  Scorsese worked with her and felt she was one of the best.

That criticism is part of what made Star Wars and Empire work; but, by the Prequels (and Jedi, to a certain extent), George is insulated from criticism and has outright "yes men" working for him (Rick McCallum).  Gary Katz had also been a sounding board and gave strong feedback and they were done.  So, Lucas benefitted from their input, yet cut himself off from it later, when he desperately needed it.  You even see behind=the-scenes footage of Spielberg visiting, not understanding anything of the story, and just saying George will make it work and people will go to it.

The book Skywalking, by Dale Pollock, really gives a great peek behind the films and into Lucas' personality and working methods.  Lucas gave him amazing access, then disowned the book, because it got too much into his personal side, showing how unplaned Star Wars and the sequels really were, how others helped him be a better director, and how running his company messed up his personal life and held back his creative life.