For some extremely loose definition of science fiction. Star Wars had fiction but no science. It is sword and sorcery in space.
Irvin Kershner, director of Empire, himself said Star Wars is not science fiction -- it is a fairy tale. It is mythology in the truest sense. Joseph Campbell remarked at length about the mythological qualities of the original trilogy, calling it a modern mythos for our time, and the primary reason for its success. It embodies many of the mythological themes that remind us of the essential adventure of life. We need good, solid human stories told in fantastic settings featuring great heroes to embolden us to bring just a little more of the fantastic into our regular lives, to be the heroes we need to be for our families, friends and communities. The original unmodified trilogy did just that and, IMO, everything since has been trying to ride the coattails of the power of that original mythology.