I think direct comparisons across eras is a really difficult thing to do. In soccer this is compounded by the fact that players of the past did not move as freely, so a guy like Pele for example never played in Europe. Most of his career, and the best part of his career, was in Brazil. I do tend to think that a player who was among the best of his era would translate, if he had access to the same modern coaching and nutrition current players do.
But would he score as many goals? Hard to say, but I tend to think not. Tactics have changed over the years, and goalkeeping/defending as improved. You look at these early World Cup games, and there were a lot of high scoring games and huge blowouts. Far fewer goals per match in the modern game:
