Erm... I remember when Space Invaders was new and there was the cowboy shootout and asteroids and them all. They were all treated as one off novelties in fun fairs for a short while until they started to make more different ones like Galaxians etc then they bunched them all together in video arcades. I think the Galaxians, Scramble, Defender era was the zenith in its history when you compare technical quality with the time line. What they squeezed out of a 1 or 2 MHz Z80 is unbelievable.