These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Awesome Music: A lot of it in this series, especially the ending theme and Henshin, Rider Black!)
Black Hole Message is one of the things that can make the words love and peace sound like a Badass Creed.
Ensemble Darkhorse: Shadow Moon remains as one of the more popular go-guys for Kamen Rider villains. So much so that he made a return appearance in a few crossover movies.
Germans Love David Hasselhoff: It's popular all right in Japan, but in other Asian regions, it's something of a childhood hero for many who were kids around the 90's, especially Indonesia, so phenomenally popular there that if any Indonesian shows are doing 'tributes' to Kamen Rider, they will be represented mainly by Black.
That's because it's the first one to be shown on TV there. It became the Gateway Series. And for Indonesia, Gateway Series are usually very well-liked.
It is also rather popular among Brazilian otaku who have the slightest notion of tokusatsu, next to RX (of course, these were the only Japanese Riders to air there).
No mention of it's love in the Philippines? Even in the present day, fans there will refer Kotaro as "Kuya Robert".
When Kotaro transforms into Black in episode 16, Ryusuke Taki calls him 'Kamen Rider', while the English-speaking Professor Smith calls him 'Masked Rider'. Ironically, the sequel series Kamen Rider Black RX would be the first Kamen Rider show adapted in America as, you guessed it, Masked Rider.
Nightmare Fuel: While not as out-and-out horrifying as some elements in some later installments, there's Golgom's disturbing tendency to almost always go after kids, and there are quite a number of scenes from the poor kid's point of view as the Monster of the Week - not as creepy as some but some are creepy enough - comes for him/her. It had to have put a lot of kids behind the couch.