@Gary Duane
so much there, easier to reply like this
As far as music analogy, I agree with the perfected thing, but that is what I think happened in tennis....each generation gets better and better athletically, diet, nutrition then sort of levels out. Certain future conditions could be seen as not progressing any further for peak athletic development in a given sport or even regressing. For example the early-mid 90s players could be seen as weak minded, soft etc. I don't think they have access to anything better or the sport is evovling anymore so the top guys are holding on. You could argue back and forth on whether that is inflating their slam count, I don't mind considering it. Although subjectively, I do think Fedovical are very, very special and unique players/athletes and see nothing wrong with considering them the best 3 of all time.
I still see a bit of on one hand you are saying how flawed a comparison is, yet you are still doing it yourself in some way.
In considering someone the best of their generation as an important criteria, you already ARE comparing different generations whether you like it or not.
Anyways, this argument seems to hold that "relative" level is important compared to one's peers. I see the logic here. But I would argue that relative level is ALREADY taken into account. Each one of Fedovical has had to beat their peers to win each of their slams just as Sampras did his. All 3 have stood out more against their peers than Sampras at slams.
The fact that it's 3 in relatively close chronological order and in direct competition with eachother shouldn't invalidate the 2 of them that don't end up as the best of their generation (invalidate necessarily as being as good as the best of a previous era I mean)
Now, I would say I think there is SOME merit to this train of though. I can see why it might be seen as "suspicious" that "the 3 best players ever" were all born in the 80s, but in my opinion they are. If I had to give a reason why, I'd say the sport of tennis has evolved to its peak just like the music analogy and these 3 were fiercely dedicated, insanely talented unique personalities at the right time (peak athletic training/nutrition/technology yet not quite yet into the soft broadband snce age 4 gen y players). You could argue that IF Sampras was born in 1980s he would also rise the same way given these right conditions. But he wasn't. In other words, we can only go by what is, not what could be. Everyone who acheives anything is basically standing on the shoulders of giants that came before them, but if you're better than that giant, then you're better plain and simple IMO.
Obviously in the case of Pete, it's not by a lot, Djokovic for example I think is just a tad greater than him as of now, but the general point I'm making is the same either way.
In the NBA, there are certain stats which ARE flawed for historical comparison, for example offense is on the rise, the pace of play is higher, 3 pointers galore. James Harden is putting up stats that are Michael Jordan level or better on offense right now. Few think he is better than Michael Jordan.
However, in the accomplishments/slams way of how we judge a tennis player a better analogy would be team success in terms of championships won. In this metric if you had say 3 great franchises, 2 of whom won 5 championships each in 20 years, and the other won 7 in a row or something, I don't think you could say the 2nd and 3rd best were worse than an all time great team that won 3 championships but were the best of their own era back in the 90s. The fact that there was so much success by a few different teams could raise questions about a watered down league (weak era) which is fair eough to debate, but again I don't get the by default being the best of your generation means you are better than someone who is not argument.