I take it you haven't seen any other Showa era tokusatsu before either? It can be a hard era to get into when you first start exploring it, since it was a time period for the genre that tended to be pretty silly even at its most serious. Combine that with the very episodic plots and dated visuals and it can be quite the shock coming from anything more modern!

I personally started with Kamen Rider Amazon, which I don't regret. It's only 24 episodes, so it isn't a massive commitment. A lot of Showa era Kamen Rider shows blur together for me because they have such similar characters and narratives, but Amazon stands out for its lizardman Rider who barely speaks Japanese and more fantasy themed plot. It looks super fake, which makes it's level of violence frankly comical instead of threatening. Has some memorable episodes too!

I will freely admit something though. I think Showa Kamen Rider tends to be notably weak compared to other tokusatsu from the same time period, even other Toei tokusatsu. I started to enjoy Showa stuff more once I branched out from Rider.

Black was definitely a hit, even before it aired. I recommend anyone who hasn't seen it yet to see this special to get a sense of the hype that was going on in '87 about Kamen Rider's return:
https://tokuzilla.net/watch/this-is-...der-black.html
And the special effects, in my opinion, are better than in Kuuga, despite the 13 year difference.

I'll go and watch the showa movies. Then I will proly watch black