Third Serve
G.O.A.T.
You can use any criteria you wish. When were both players consistently delivering the best matches? When were both players in very good form? When did they play most of their matches? Which time period was more enjoyable for you as a fan of one or both players? It could be 2007-2009, 2011-2012, or other years.
How about Federer-Djokovic?
Djokovic-Nadal?
How about Federer-Djokovic?
Djokovic-Nadal?