Here's the thing: Lucas created next to none of them. They were either loosly inspired by/liberally ripped off of some older work (see Flash Gordon, Buck Rogers, the countless Kurosawa films and war movies he ripped off) or changed radically by the multiple edits made along the way that as much credit is owed to Spielburg, Kasden or Marsha Lucas as there is for George.
Lucas created them. All work today is derivative of previous work. It's called inspiration. Flash Gordon is a ripoff/inspired by Buck Rodgers which itself is based on swashbuckling and space fantasy novels from the 19th century like Jules Verne, H.G. Wells and Edgar Rice Burroughs. Batman is a ripoff/inspiration of the Shadow; Superman is a ripoff/inspiration of Hercules. I haven't seen Kuwosawa films yet, but I'm pretty sure they were also inspired by previous archetypes.
You want to know what we'd have gotten if people hadn't shot down Lucas every step of the way on the road to Star Wars?
Nobody shot down Lucas. People who have been interviewed, such as Anthony Daniels who played C3P0, have said that Lucas was hardheaded to work for and that he was determined to do things his way. Lucas was willing to solicit and ask for others' opinions (like many other writers and scenarists do) but whether Lucas was to incorporate them or not was entirely his call. The only person that was willing to stand up to Lucas and have his/her way was his wife, Marcia, and she was only partially successful. For example, it was her idea, against Lucas's will, to have Leia kiss Luke and wish him luck before they were forced to a perilous swing across a chasm in ANH. But that's it. Even she constantly found it draining to have her way. The rest of the movie was all-Lucas.
The plot would have been a much more liberal rip off of
Hidden Fortress. The Jedi Bendu would battle the Sith over control of the Bogan Force. Han Solo was a reptilian pirate who hunted wookies. C3PO talked like a used car salesman. Vader was almost entirely off screen, with a charachter named
Valorum taking his place as the lead villain. Luke Skywalker would have been an old man, while his padawan Annakin Starkiller would have been the protaganist. The dialogue is largely clunky, wooden exposition.
Look over the scripts, than thank whatever deity you choose that Lucas didn't get his way.
That was the first draft. Lucas was constantly changing plot points here and there thoughout the drafts, searching for better storylines. He was quoted as saying he had written 4 different Star Wars storylines before deciding on the one he liked the most. It was Lucas HIMSELF who eliminated the Valorum character, who only existed in the first 2 drafts, and it was Lucas HIMSELF who changed Han Solo into a human by the second draft, and it was Lucas HIMSELF who changed all other character points and plots you mentioned such that by the time of the revised fourth draft, it was the one we saw in theatres.
The problem is he made a Howard the Duck movie PERIOD.
Go on the website. Many people, including many Howard the Duck fans, claimed that it was an underrated film hampered by the fact that it was live-action. If it had been animated, like Lucas wanted but couldn't because of contract obligations, the film would have been better received instead of being laughed at because of how ridiculous Howard the Duck looked live-action.
Same reason why we don't have a successful franchise based on Flash Gordon or John Carter - Star Wars beat them to the punch. Disney only cared about the brand name.
Or maybe Star Wars is just better. Flash Gordon has existed for decades but never stood the test of time. Star Wars has.