Project Zeorymer

Both are Mecha series where the main character is thrust into being a pilot and having to defeat numerous other similar mechas. The action in both shows is beautifully drawn and animated, and while their plots mostly serve to link the battles together, they both feature stories that lead the MC to question their own reason for existence and why they even fight. 

These '80s OVAs have similar mecha-themed plot elements, characters and music, and they are directed and produced by the same people. Zeorymer is like a darker and edgier version of Dangaioh. 

Both feature plots in which the main characters have to fight alone against numerous mechas similar their own, with really great animation during the battles. Both main characters also have issues regarding their fathers, although the way they're implemented is quite different in each of the shows. 

Both are super robot anime with a dark tone about a boy forced to become the pilot of a giant robot, as well as a conflict between a clandestine government agency and a secret society. 

These two shows are both on the darker side of the super robot genre, focussing on the flaws of the hero and the thoroughly broken characters surrounding him. Ayato is distinctly more likeable than the protagonist of Zeorymer, but no less disturbed. 

Different theme and elements, but give a similar feeling because Tetsuo Shima and Masato Akitsu are mostly controlled by the greed for more power and parts of the plot are also similar.