Battle Beyond the Stars is more like Seven Samurai in space, and we'll have it on Blu Ray before the OT.
It's a little unfair to lump Galactica and The Black Hole in with the obvious rip offs, as both were being developed long before Star Wars even came out. Of course, SW is what got them finally greenlighted.
And Fox was so lawsuit happy at the time, they wanted to even go after Hardware Wars, but Lucas liked it. I'm surprised the owners of Flash Gordon didn't think about suing Fox. After all, Lucas pursued the movie rights before making up his own space opera!
The mother of all rip offs has to be The War in Space. Quickly conceived after some Toho studio people saw Star Wars in Hollywood, and released in Japanese cinemas before Star Wars! The horned Wookiee ripoff with the battle axe still cracks me up to this day.
Where were you in '77?