Great points El Dude, however, I will say , doesn't ending YE #1 trump who had more weeks #1 during a calendar year? After all , Novak may still trail Federer technically on Weeks #1 but he's already passed him with 6 YE#1's (counting this year) something only Pistol Pete managed in the Open Era. So in that sense I would rate Novak higher than Roger already on that front.
Ditto If Rafa can snag at least one more YE #1 to get to 6, in some ways that surpasses Rogers weeks simply because he has one more year then Roger's 5.
Personally I think Rafa getting to 5 USO's is better than getting the 2nd AO simply because he then ties the record, along with Sampras, Connor and Federer of most USO wins in the Open Era.
I still think Roger's most impressive stat that the other 2 guys won't match is 3 years with 3 Majors won. 2004, 2006, 2007.
Aren't stats fun?
While stats are objective measurements, ultimately how we weigh them is subjective. YE #1 sounds flashy, but I think weeks is more meaningful. A year is, after all, rather arbitrary. On the other hand, I suppose you could combine the two to get two sides of the same picture.
Of course even weeks at #1 has its problems. Few folks would suggest that Roger Federer wasn't the best player of 2017 though he finished #2 due to skipping clay season, and of course Andy Murray won the 2016 YE #1 largely through an approach of quantity over quality. Rafa lost a lot of weeks at #1 due to injury--especially in 2009-10--even though he was the best player on tour during that time. Etc.
Again, entirely subjective, but in my mind you could categorize accomplishments in tiers, depending upon how primary they are to measuring overall greatness:
Primary: Slam titles, #1 rankings (weeks/YE).
Secondary: Overall titles, YECs.
Tertiary: Slam results (other than wins), top 5/10 rankings, Masters titles, head-to-heads, etc.
And then there are things that don't fit into any tier, like the feat you mentioned that Roger accomplished, or Novak's 2015-16 stretch, or Rafa's 13+ Roland Garros titles.
It just isn't an exact science. We can build arguments and create formulas, but ultimately we have to rely upon our own judgement. It may sound like a cop-out, but I think they are--and will be considered, historically speaking--coeval GOATs, almost no matter what happens. They all reigned supreme for a time, all dominated their peers, and all have their own unique flavors of greatness. For instance, I would say that Roger stands alone in terms of peer dominance - he dominated his own generation unlike anyone else. Rafa has his clay dominance and unparalleled level in clutch situations, and Novak probably reached the highest level of all, virtually unbeatable at his very best.
All that said, accomplishments stand on their own. Slam titles are objective - the player who finishes with the most (my bet being on Rafa, with Novak and Roger about equal) gets bragging rights for the most important stat of the Open Era. Weeks at #1, YE #1s, titles, etc. They all stand on their own, and all three are going to end their careers with some truly remarkable accomplishments and the three most impressive resumes of the Open Era.
