It is short sighted and foolish to really think head to heads between greats are completely irrelevant. No Nadal with 6 slams does not rank higher than Federer with 15, but to think that matters none in elevating Nadal and to some devalueing Federer is simply not true.
Here is one example. When you compare the careers of Navratilova and Evert, Chris has the edge in virtually every discinerable way before evaluating head to head play. Far more longevity (longevity of 13 years close to your best matters much more than 5 years close to your best and an added 15 of just pretty good play), miles better consistency, more versatility across the surfaces, while not the same 2-3 year level of dominance, similar dominance over a 5 year period. Chris also missed out on having many more slams than Martina, and likely more than Graf but the WTT commitments of the 70s. Yet nearly everyone now ranks Martina over Chris. Why? Martina dominated Chris for several years when Chris was still close to her best, and their careers are still close enough that this sways the favor to Martina in nearly everyones mind, despite that overall it is Chris who had the better career in singles.