To address each in turn.
Open Era - This primarily effects Laver and Rosewall, but also Newcombe and Ashe, all four of whom are "tweeners." There are two ways to do this; either look only at Open Era results or look at their entire careers. I choose the latter, because I simply don't think it is fair to those four to only look at their Open Era results because it doesn't accurately depict their overall greatness. But this is a personal choice. If I were to rank them on Open Era results alone, obviously I would rank them differently.
McEnroe vs. Connors. There are several troubling areas in ranking this list and one was in what order to rank Mac, Connors, and Lendl. I think Lendl tends to be underrated historically, that he had a similar peak to Mac (if never a year as great as Mac's 1984), but with a longer prime and thus gets the edge. As for Connors, he has slowly gone down in my estimation the more I look at his career in detail. A great player, no doubt, but some of his year YE1s are questionable - for instance, Vilas should have been #1 in 1977 and probably Borg in 1978; I think you can make an argument for Ashe in 1975. Furthermore, a ton of Jimmy's titles are really low level stuff. But in the end, it could go either way.
Chang vs. Muster. The fact that you and Ricardo are debating it out supports my view it isn't an "obvious flaw." Again, my point is not that you are incorrect, but that you are being just a tad hyperbolic. Chang and Muster are pretty damn close, and it really depends upon how you want to weigh things.
I played tennis in my teens, and some of us were taken to Wimbledon each year to watch the championships.
