I've been known to Lucas bash, as plenty of bashing is deserved. But the whole idea that Star Wars could have existed without him is truly a silly claim to make. The man makes shit up and constantly changes his own history, but there was a time when he was a promising young director/story teller with some really great ideas.
THX-1138, American Graffiti, and Star Wars were all pretty good films. I've often felt it is a shame that after this point he got caught in a SW rut. I feel like the popularity of Star Wars and the commercial possibilities of it took over and smothered out the man who could have gone on to be one of the better directors of the 80's and 90's. From there is was all Star Wars and a few poorly done flops on the side.
Sometimes I still wish Star Wars had been far less successful, becoming an eventual cult classic, with George going on to make more films on par with THX and Graffiti.
No matter what you want to say about him, the man had creative talent. Maybe those three good movies he made did have other creative talents and influences propping them up and making them work, but George did play a large role in all three of those films. And Star Wars, from the first film in '77, to the two sequels, along with all the baggage, good and atrocious, that followed, wouldn't exist without him. That isn't revisionist history, that is a solid fact.