There were a lot of Galaxian clones on pre-NES consoles and computers. Some of fhem were close enough to be sued over, but there was one I liked on TRS-80 called Galaxy Invasion. That one had the twist that the boss "flagship" enemies would occasionally fire unavoidable lasers if you didn't destroy them in time. There were no official Galaga ports until the NES, so I think Galaxian actuallly did better on the home market since Galaga had to compete against Super Mario Bros. It's obviously a different story now: Galaga is one of the most evergreen arcade games out there and is in almost every collection Namco puts out, alongside Pac-Man and Dig-Dug. Galaxian occasionally gets put in colllections for historical context, but really shows its age while Galaga is a legit timeless classic.
I always thought of early 80s shooters as falling into one of three categories: Space Invaders clones, Galaxian clones, and Centipede clones.



