You'd have something else, but it wouldn't be Star Wars.
I'm not interested in something else. The Last Starfighter and Star Trek:TMP are decent films, but I don't own either and I certainly wouldn't be on a forum discussing them. I'm here because we got Star Wars, with every single frame that we saw in 1977.
Even to this day there still hasn't been anything close to Star Wars. Nothing with such scope and humour and imagination in a sci-fi world that incorporates fantasy. 2009's Star Trek and Last Starfighter--the latter of which clearly would never have been made if it were not for SW--are the closest. But they don't come close!