Jungle Taitei (1989)

I like both of these in a way, and I believe they are both good insights into what Japanese animation was like for the non-famous anime, back when they were made. 

Both series started and ended in the same year and have the same number of episodes. They have a very similar atmosphere and animation in some places. Even though they are made for children, there are still sometimes quite dark and deep things in them that very young children may not understand. They are also not afraid to show a little violence. Also, both of these are, at least in the undersigned's opinion, even better than the original 60s adaptations.