What got me interested in the franchise as a whole was actually the much more recent series Casshern Sins, which is only very loosely based on the original series. Casshan and Casshern Sins appeal to me in different ways. A lot of Casshan's appeal is simple entertainment. I like the way it looks and sounds, and I like seeing Casshan defeat the enemy of the week using his distinctive acrobatic fighting style. But what really draws me to Casshan more than most series like it is the travelogue aspect of the show. I love seeing the effect that the conflict between Casshan and Andro Force has on civilians and how those civilians affect the conflict. It's not all that ambitious, but it makes Casshan more interesting than the average action anime.
I'm only six episodes in, but I do like the fight scenes. They really try to make Casshan look equal parts strong, agile, and cunning and despite some flaws in the animation, they really pull it off. I've never seen the '70s Spider-Man cartoon, but seeing as how he's supposed to have similar traits, I wonder how well the two compare. I haven't picked up on the travelogue aspect, but I will say that I think their choice for aesthetics is very interesting. Everything from the architecture to the design of the robots to the clothing the extras where all really have an early 1900s Eastern Europe vibe going for them. It's an interesting choice.