One can argue there was a dry spell of fantasy and space based sc-fi in the early to mid 70’s. There was only one Ray Harryhausen film in this period, The Golden Voyage Of Sinbad in 1973.
Most science fiction films before 1977 were of the future dystopian variety, Soylent Green, and even Logan’s Run. Not sure if Flesh Gordon counts as an sci-fi film. In the same year as Star Wars, Fox was giving us post-apocalyptic tales like Wizards and Damnation Alley.

I have to give Toho studios credit for cranking out The War In Space and getting it into theaters in Japan before Star Wars even opened there. The story goes some Toho executives saw Star Wars playing at Mann’s Chinese Theater while on a visit to Hollywood that summer, and were hatching plans on the plane ride back home.

Seriously, how did Fox not sue over this guy? 😛