But if you accept Guardians of the Galaxy as a super movie, does that also mean that Star Wars is (since you have people using super powers, i.e. "the force")?
Yes. And it's a sub-genre of science fiction. Also include Buck Rogers, Flash Gordon, Tarzan and Sherlock Holmes (?). Superman started the sub-sub genre where they wear long underwear.
As super villains go, Darth Vader is Dr. Doom in space.