Star Wars has never seemed like science fiction to me. Its fantasy, It's not based in fact, its all fiction. Star Trek, Soylent Green, Planet of the Apes, hell, even Flash Gordon is Science Fiction, its all with humans and stuff... But Star Wars is pure fantasy. People who change their oppinions of Science Fiction because of a Space Fantasy like Star Wars are like people who change what they think of Nature films because of Lord of the Rings...
You can't put something like Stargate up against Star Wars because with Stargate (or even Alien or Terminator) its like, "This could happen to us in the future", not, "this could have happened a long long time ago, in a galaxy far far away".