Devilman

The concept of "good versus evil" has been covered in media for quite some time, and these shows are no different! Both feature different and unique villains opposing the main character/s, while also including a lot of action with the thematic good versus evil. The hero/heroines in both shows have to hide their "true" appearance for the general public in order to save humanity. 

If you're a fan of early Toei anime, I'd definitely recommend Ryu to fans of the '72 Devilman and vice versa! Both are animated in the same way and both have the similar a bit repetitive plot at times. Also Ichiro Mizuki sings the banger openings of the both series! 

Both of these Go Nagai works are similar in that they are episodic super hero shows where the main character is constantly fending off foes who threaten humanity. They also have a similar art-style and the voice acting has that same static-y effect. The aliens designs in Gaiking also really remind me of the designs of the demons in Devilman, they're just a little bit more sci-fi looking. 

Yuu Yuu Hakusho is a great series after watching Devilman or before it. Both series have some similarities and also they both have that old anime feelin'.(Because they are old) -It is playing sometimes in a school -Schoolgirl(s) -Crazy old jokes (that you probably will never understand) -Powerful Antagonist -Supernatural creatures 

Both are episodic horror classics that usually consist of demons attacking students. They can also flip between comedy and more serious moments but Devilman can be very repetitive. 

Both are Go Nagai series featuring a brutal hero who battle monsters and demons. While the structure of both anime can be repetitive, they do feature very odd character designs and many unforgettable moments. Cutey Honey is the more colorful of the two but contains the same level of violence as Devilman. 

Both the 1970's Devilman TV series and Guardian of Darkness follow a protagonist who has a demon inside a human body. Both anime are action-packed and have the main character able to grow bigger to fight other giant monsters that are constantly attacking other people. They both must protect a female love interest (Miki in Devilman and Terumi in Guardian of Darkness). If you like, you should like the other. 

they have similarity themes of apocalyptic events ... however the characters plot focus good within evil .... meaning to say that the story is focusing in the bad side that making it good side .. opposite in reality on what we learn in our society... 

Both Nagai properties were worked on contemporaneously by the same studio, and it shows. They're animated quite similarly (stiff figures, bright colors) and both feature a simple monster-of-the-week plot. I'm relatively sure that the two shows even share actors; Kouji and Akira are essentially the same character. 

Both titles have the protagonist that can transform into a demon monstrous form and uses their power to fight for good instead of evil. The SoulTaker has a design that looks pretty similar to Devilman. They both feature supernatural elements with lots of action and blood. If you enjoyed Devilman or looking for another demonic theme superhero, I recommend trying out The SoulTaker. If you enjoy The SoulTaker, feel free to give Devilman a try.