Christopher Reeve did such an amazing job that to give him some kind of accent or more bravado would have been wrong. Audiences wouldn't have responded to that either. ↗
My own dreams fortunately came true in this great state. I became Mr. Universe; I became a successful businessman. And even though some people say I still speak with a slight accent, I have reached the top of the acting profession. ↗
For whatever reason, we relate to anything godlike with an English accent. The English are very proud of that. And with anything Roman or gladiators, they have an English accent. For an audience, it is an easy trick to hook people in. ↗