Shinzou Ningen Casshern

Both are classic and influental anime superheroes by the same studio and creator. Both features superheroes that wears helmet and rides on planes and vehicles. Both features alot of melodrama and action 

Both are original Tatsunoko property and old episodic TV series about a teenager fighting in the purpose of taking vengance for their families. Both Casshern and Sanshiro also voiced by the same voice actor  

Both feature a wanderer in a future wasteland who fights to protect the weak by making his opponents explode. Both also have very creative (if limited by budget) fight scenes, and as a bonus, the villains Braiking Boss and Raoh share a very intimidating voice actor. (Actually read Hokuto's manga, it's way better, but we can't rec manga to anime really. Casshern has no manga.) 

Casshan & Devilman are superheroes who sacrifice their humanity to wage war against evil. These heroes fight out of love for their parents but are feared by humankind. The only people who accept them are their girlfriends; Luna & Miki.  

Both are about humans who, through different means, become super-powered cyborgs. Both series have the characters fighting crime and evil. This was a big theme in the 60s with the advent of technology, especially of the robotic type.  

Both feature a similar level of action, violence, and even similar characters but Casshern is significantly more serious in tone.