What exactly makes an athlete so much better today than 30 years ago? It can't be genetics or a better gene pool, since there has not been enough time for evolution to occur between then and now.
I might throw out an idea that athletes today get better equipment, shoes, training (not necessarily better coaches, because there were some awfully good ones back then), year-round work outs, better nutrition, better supplements, etc. Can you imagine what Dave Winfield in his prime would be like with the things that are available to athletes today to make them better? It is scary to think about!
That is why we see track records and swimming records constantly falling. They likely aren't much better genetically, but they are trained better and have more completely reached their potential because of it. Again, just imagine Jesse Owens, Barry Sanders, Pete Maravich, Walter Payton, Jim Brown, Wilt Chamberlain and Bill Russell if they were in today's sport scene.
This post pretty much hits the nail on the head. The athletes now aren't "better", they just have more stuff available to them. But saying Bryant Allen is on Dave Winfield's level....what??? LOL