One major difference. George Lucas didn't give interview after interview suggesting that Star Wars was, in fact, real.
Dan Brown wrote a work of fiction, sold it to publishers as fiction but then began stating that the information in the book was true.
BIG difference.
"BIG difference."
I understand your point, but I disagree on the impact and motivation. It's just marketing at its sleaziest, no different than Alex Haley (sp?) claiming that Roots was actually based on his ancestors' experiences.