One title that instantly comes to mind for me is Genesis of Aquarion. I admittedly never got very far into it because it’s really awkward to watch with other people around (looking at you mecha combining scenes). I actually really only checked out the show because I heard the OP in Taiko no Tatsujin Portable DX.
Anyway, the song is also called Genesis of Aquarion and is by AKINO.
I’d have to pick Butter-fly from Digimon Adventure.