You know, that's a really good point about all these continuing stories. Star Trek was very much the combined efforts of many people, as were the first two (and only good) Star Wars films. This "vision" business is a code word for "successful formula we desperately want to replicate to make a bunch of of money but we'll talk abuot it like a religious dogma to appease the diehard fans". It always ends up being restrictive and ultimately kills the vitality and creativity of a fictional universe.
It was actually a similar conversation about Lucas that prompted me to dig up the dvds and rewatch them.
I'm not sure if it is a recent development but certainly I've noticed alot more of the Lucas-is-a-genius stuff in recent years than ever before. (Although I have noticed this word bandied about more frequently in general with other people too)
Still, especially after watching some of the special features it sort of seems to me comparable to giving Pope Julius II the credit for painting the sistine chapel.
Whatever creative limitations Lucas has, it really can't be denied he is one of the rare few who pushes forward the technical side of cinema with a very tangible result (computer controlled cameras, THX sound in theaters and at home, ILM, digital cameras/film, etc). For that reason he is probably more important than Spielberg, despite his much shorter list of director/writer/producer credits.