Results for the past three seasons (2012, 2013, 2014)
Murray - WIM F-W-QF, Olympics W, 1 Queens title (2013)
Djokovic - WIM SF-F-W, Olympics 4TH
Federer - WIM W-2R-F, Olympics 2ND, 2 Halle titles (2013, 2014) + another final
All three have 1 Wimbledon and 1 extra final. Essentially a tie.
Murray won the next best event, so he's undisputably the best, plus he has a Queens title too.
Federer came second at the Olympics, so he should be next, and his Halle titles easily cancel out Novak's slightly better non-title Wimbledon consistency.
Novak didn't medal at the Olympics, and has no extra grass titles.
Murray has been the best, then Federer, then Djokovic.
This really can't be argued with.