I don't think they would. Just like Jim Brown wouldn't be nearly close to what he was in the NFL today. If you took the athlete from that era, exactly what they were, how they developed, etc...and put them in today's game, they wouldn't make it.
Today's athletes are faster, stronger and move much more efficiently.
Skill-wise, maybe...but I suppose the context someone takes with the question.
In 20 years, the 2035 version of athletes will be better than almost everyone from the 2015 era, no matter how great the 2015 guys were.