I used to watch this show all the time as a child, and for some reason the other day I thought of it. It was such a distinctive show that I can still remember particular scenes even though I haven't watched an episode in years. What stuck with me was the real graphic tragic nature of many of the episodes. Children's parents would be transformed into monsters which Spectreman would kill, but only with great sadness. Spectreman himself would go through all sorts of trials and tribulations. Blindness. Sickness.
What was innovative about the whole show was the idea that the villains, these ape people from space, created monsters from the pollution or evil of the earth. These creatures were mankind's own failings come to life. It wasn't just about a giant robot beating up on space invaders, as many Japanese cartoons are today. In this way, it is similar to old Godzilla shows (though I think Spectreman may have come first?). That's what Hollywood missed with their adaptation of Godzilla, this whole idea that Godzilla arose from mankind's nuclear waste as a symbol of the perversions which are possible with advances in technology, and science.
The Japanese have a very strange love-hate relationship with technology. It's fascinating.