Just to clarify on that Jetzons thing, that wasn’t a ripoff, that was the Jetzons composer using his own composition twice - sega paid him for some tracks alongside michael jackson.
@jeelz just posting a bare youtube link will embed it. (also light crusader rules, and I had no idea about this composition similarity!)
There are some pretty famous game-on-game ones, notably Jim Power:
really bare-faced ripping off Ys 3 (he said he must’ve done it unconsciously)