I try not to compare male and female sports people. I tend to separate them for the purpose of 'greatest ever' arguments.
I'm having difficulty trying to explain why; I guess it's just hard to measure.
Personally I find Federer to be the far more accomplished tennis player. He's basically perfected every aspect of tennis - he's graceful and precise in everything he does from hitting clean winners off both wings, to deft defensive slices, to impeccable volleys off his toes, a great serve, and so on.
Federer can beat you in many ways because he has all the tools.
Serena however tends more to overwhelm her opponents with her power and superior physical attributes.
And yet, she's won more Slams because she's much more of an outlier in the womens game with her power and athleticism giving her an overwhelming advantage over her opponents.
So is Serena being that much better than her rivals - as opposed to Federer - that much due to her own greatness or because she has less comparative competition?
I think it's more the latter. She had one truly great rival during her career - Justine Henin - but that's it. And for the record Serena wasn't nearly as dominant during this period.
How would she have fared in terms of Grand Slam wins if she had to face 3 Henin's over the last 10 years (the equivalent of Djoker, Nadal, Murray)?
I'm rambling now, largely due to the difficulty in comparing men and women
I will say that Serena is the greatest sportswoman of all time though. Katie Ledecky is probably the other freak of an athelete that is on her level and may surpass her.
