There's much wisdom in this post.
Playing conditions haven't changed much in the past twenty years and I'm not convinced that the equipment has advanced very far, either, but to compare the players of this generation to those that played alongside Earl, Sigel, Varner, and Hall is a bit problematic because the game itself has changed.
Last November, Mike Sigel and I had a chat about how the stroke needed to succeed today is different than what was needed some forty years ago. He noted that the short, compact stroke that is in vogue today reminds him of that of Allen Hopkins in his prime. I think that equipment has evolved to suit the players (and strokes) of this generation, and that the equipment of forty years ago was perfect for that generation of players.
All that said, your premise is correct. Ultimately, the comparison across generations is almost impossible, and in the end, excellence can only be measured in the context of how any player performs against his/her contemporaries.
Thanks for your input.