Federer by far:
* Beautiful tennis
* Excellent on-court demeanour
* No time wasting, no cheating, no fake medical timeouts, no desperate tactics
* Pretty hair
* Beautiful twins
* Intelligent interviews, funny, relates to the crowds
* Mega marketing machine
* Decade of brand building
* Legend status
It is hard to compete with Fed overall...
Murray - often appears grumpy/angry on court and seems very awkward in interviews, sometimes looks/sounds like tennis is too much effort
Nadal - dubious routines, time wasting, gamesmanship and awkward interviews, grunts
Djokovic - Slow start to his career in terms of always being seen as a tier below (until recently), used to have a lot of medical time outs, withdraws. Has been hostile to crowds in the past. Grunts. Rips shirts etc...
The only negative some people might see in Federer is what they perceive as "arrogance" which I don't believe myself. I think he's just honest and mostly says it how it is. I'd rather that than false modesty