Well Pete had to go against Becker, Agassi, Courier, Goran, Rafter among others to get his wimbledon titles..
Thats a star studded cast of talent right there.. While Fed goes up against baby Nadal, Roddick, Murray etc. Not quite the opposition that Pete had on grass.
Then you got Nadal on clay.. Who outside of Djoker and Fed (who are pretty good dirtballers but neither great. Both their weakest surface) didn't have much to contend with in terms of great clay competition.