I think I remember reading that Toei ditched the Space Sheriff idea after Shaider because ratings had gone down. Juspion was an attempt at keeping a similar visual look but having a different approach to the story, ditto for Spielban. I think there would have been a much more solid brand identity had they kept that basic look going but then we got shows like Metalder and Jiraiya that were just so incredibly different from each other and the first five Metal Hero shows that everything pretty much went out the window.
It seems to be that the one really prominent feature to the franchise is that they were typically part of some sort of law enforcement agency. You had nine or so series out of 16 that are linked to the idea of being a cop of some sort. You have the first three series about space cops, then four that do their own thing and then six more shows in a row where the heroes are some sort of cops. I'm not sure why this theme never became widely seen as its brand, but I've thought that the radically different visuals while keeping a certain unifying theme was sort of like Metal Heroes' version of what's happening with Heisei Rider, really different looking heroes from series to series but a general thematic unity is usually there.
I am still confused but thank you..
Pretty much like what's been explained, Metal Heroes is the name of a franchise, not really the name of a genre within tokusatsu. Tomica Heroes was from Takara, the Sazer shows were from Toho, each had their own specific themes, the Tomica Heroes generally fought disasters and had giant vehicles while the Sazer shows revolved around giant "star god" robots. It's not like kaijuu films where there can be a ton from different companies, each franchise is owned by a different company and has their own unique traits.