If you're looking for anime similar to Hyakujuu-Ou GoLion, you might like these titles. All recommendations are made by Anime-Planet users like you!
In the 21st century, the evil faction known as Galactor is set on world domination… and there’s only one group of people who can stop it: the Science Ninja Team! Under the guidance of Dr. Nambu and the International Science Organization, the team handles everything from taking down giant turtles to battling iron monsters, all in the name of justice! Go go Gatchaman! Take down the evil Galactor and save the world!
How does one start the similarities?
A team of 5
They fight against overwhelming odds.
Both have a hero vehicle of sorts. In Golion(voltron) It is 5 armored mecha resembling lions, that can combine into a giant singular humanoid mecha.
In Gatchaman (Battle of the Planets) the team has one giant singular ship that has mini vehicles inside of it (such as a smaller fighter, a rolling 4x4 and a motor bike)
both series the cast is dressed in a Ccrayola box of colors.
part of a classic genre of episodic action tales. Both are very similar.
Shiba, a famous scientist, has been horribly murdered. His eldest son Hiroshi, a famous car racer, soon discovers that his legacy still lives on - and is threatened by the revival of the Evil Empress Medusa, the female demon who ordered his death. Along with his best friend Miwa, Hiroshi becomes the head and soul of his late father's ultimate creation: Koutetsu Jeeg...
There is a web of shows that have a hero machine, but these two share more in what they fight.
Both titles have large beasts that the hero mecha has to fight, that are more on the magical side.
In Golion it is more a team, in Koutetsu it is more a pair. But there was a combination sequence much like Golion(Voltron). Except the pilot in Koutetsu who actually transforms into the head.
I originally saw Koutetsu as (El Vegador) and Go Lion as Voltron, but the similarities are very much the same.
The series centers on Mars, who was sent as a baby to Earth with the eventual goal of destroying it. However, after being adopted by a Japanese family and given the name Takeru, Mars grows up experiencing the beauty of the planet and its inhabitants, and he questions his mission. Mars uses the powerful robot God Mars to protect the Earth from his people, even being forced to fight his own brother.
Both are early 80's anime that feature mechs that combine to form a larger mech. In both series, the heroes go against an empire led by an evil tyrant. Of course, there are some differences (such as the fact that the mechs in GoLion are piloted by a team, while in God Mars the six robots are all controled by one person. Also, God Mars features psychic/superhuman powers about as much as the mechs, while GoLion does not). Stiil, if you like classic combining mech anime, then you will probably find something to like in both series.