When Federer's career started, he had to deal with "old man" Sampras and Agassi who, while a good player, was never a great player. For his first GS, he beat Mark Philipoussis in the final, which is sort of similar to Djokovic beating Tsonga for his first ever GS title. Andy Roddick was also there or there abouts, but as far as great players...
Fed's second GS title was Aussie open where he beat Marat Safin...Safin is the equivalent of Grigor Dimitrov today...hyped to the max without any results. Djokovic beat Murray for his 2nd GS in Australia. Murray was considered Top 4 with Rafa/Fed/Nole....
So, if you're saying Nole's only competition is old man Federer, then its fair to say that old man Sampras was Federer's only competion when he rose to the top.
for his 10 GS titles so far, Djokovic has gone through 3 guys: Federer/Murray/Nadal with the exception of his first GS win.
in his first 10, Federer went through: Philipoussis, Fernandez, Roddick, Safin, Baghdatis, Hewitt, Agassi and Nadal.
first 10 for Nadal: Puerta, Berdych, Soderling, Federer, Djokovic
Not trying to slight him at all, in fact, I respect the hell out of Federer, but starting out, he did benefit by a transition of sorts in mens tennis.