So I was browsing around yesterday and I found this video.
Do we know anything more about this game (other than it was never released)?

From what I can tell, this was made by Nichibutsu or maybe its third party dev-team Make Software (Terra Cresta II, Power Gate, Chip & Dale 2, Ducktales 2 etc.).
 

Ive only ever seen a few screenshots from old Famitsu magazine. Great to see this video, it seems like the game was FAR along with some complex animations!

It was shown in the Japanese magazine Famicom Tsushin No. 10 and 11 in 1990, the only thing that is that the main character is a God who must conquer different parts of the world fighting against other gods, counting as help monsters or beasts that evolve, apparently in a similar concept to the Pokemons.
The name of the game would be translatable to Mythical Beast Genesis.