Kouchuu Ouja Mushiking: Mori no Tami no Densetsu

Mushiking shares the same character designer [Yoshihiko Umakoshi], director [Shigeyasu Yamauchi], music composer [Kaoru Wada], sound effect designer [Tooru Noguchi], writer [Ryuu Kamio], and series composer [Reiko Yoshida] as Casshern Sins. And you can really tell within minutes. They're basically the same show. Coming out a few years earlier, Mushiking is the proto-Casshern Sins. If you love Casshern Sins, you will love Mushiking. Sub recommended. 

Although the genres of these shows are quite different, they also had a lot in common. Both shows had strong focus on parent/child relationships. Bashin and J have aesthetic similarities to Popo and Soma, respectively. Soma and J have story arcs that are very similar as well.  

Both are fantasy series with a very mysterious atmosphere. They also both involve giant fighting bugs.