Ohmigod, how have we forgotten this one?
HIGHLANDER was a basically a sword-and-sorcery adventure set in modern times and ancient Scotland. The sequel, HIGHLANDER: THE QUICKENING, was this weird, futuristic, scifi thing that insanely retconned the Highlander into an alien from another planet!
Along the same lines, you have THE BEASTMASTER, which was pure sword-and-sorcery, followed by a sequel, BEASTMASTER 2: THROUGH THE PORTAL OF TIME, which had brought the hero into modern times for a more scifi-tinged adventure.
(Just to complicate matters, the first movie was very
loosely based on a novel by Andre Norton, which was science fiction, not fantasy.)