Actually it was the Brazilian release that called it Gang's Fighter; Europe, Australia and Portugal all called it My Hero with the latter having an interesting cover.

Most (not all) Brazilian releases kept their original name on the title otherwise we would talk about the missing title screens of Enduro Racer / Super Cross, California Games / Jogos de Verão (literally means Summer Games that's a completely different game, not to be confused with the later revision Game Box Série Esportes Radicais that DID get its title changed but only keeping 2 events), Tennis Ace (ditto with Super Tennis), Putt & Putter / Minigolf, etc. I actually wondered how many Brazilians got confused when they played on their Master Systems with the game having a different name and thinking something was wrong.

They also apparently didn't bother changing the title screen with the European release "Gang's Fighter".

They could make the title screen blue but not the fucking sky?!