Federer - dominated his peak but has some very questionable 00-03 losses (at which age Djokodal were making Slam finals) and then had issues post 2009 dealing with younger ATGs. Then again, Berdych knocked him out of 2 slams in 2010-12…
Overall I think Fed is a victim of playing too long for stuff like H2H. He was great even at an old age.
Djokovic - not as mentally strong as advertised but let’s give some context. WB 2013 - dead after DelPo match, USO ‘12 - wind and just overall awful conditions, USO ‘16 he played the easiest draw maybe ever and was semi hurt/out of it.
I think Djokovic got to a fair amount of finals where his form/fitness wasn’t really at a slam winning level and then just hit a wall. Aka last weekend. But overall Wawrinka really hurt him in his prime which is something the other two don’t have.
Nadal - if Nadal is not fit or fully firing, he will either skip the tournament or lose before the quarters, pretty much always. If he is fit and on form he’s always a contender. As a result he has a better Slam H2H, finals/SF record etc. but in all actuality those numbers are a bit inflated, as he loses early or simply skips tournaments which the other two would play through.
Overall I think Murray/Stan’s level were underrated and I feel for Djokovic a little, as Stan got Nadal and Federer in 13-15 in Slams as well. But yeah, this (and especially the Nishikori loss) is why I can never say Djokovic is unquestionably GOAT. Too many weird losses in his prime.