I just read an interesting article about the greatest tennis seasons of all time.
Who had the greatest season ever: Federer in ?06 or Djokovic in ?15? | For The Win
The article picks the six best tennis seasons according to a player's winning percentage and then compares them. It eventually comes down to 2006 Federer and 2015 Djokovic. The author gives 2006 Federer the edge, because he had to face Nadal on clay and hence lost the RG final, while Djokovic faced a "less difficult" opponent (Stan Wawrinka) in the final, but lost.
A comparison of their seasons:
* 3 Grand Slams: Australian Open, Wimbledon, US Open (RU at RG)
* 4 M1000 titles (out of 7): IW, Miami, Toronto and Madrid. (RU in Rome & MC) + WTF
* 2 ATP 500 titles: Tokyo and Basel (RU in Dubai)
* 2 ATP 250 titles: Doha and Halle
*52 weeks at No.1
*3 Grand Slams: Australian Open, Wimbledon, US Open (RU at RG)
*6 M1000 (out of 9): IW, Miami, MC, Rome, Shanghai and Paris (RU in Montreal and Cincy) +WTF
* 1 ATP 500: Beijing (RU in Dubai)
*52 weeks at No. 1
For me it's 2006 Federer, because he was more dominant in his GS victories and he played his best tennis that season (imo Novak played better tennis in 2011 than 2015.
Edit: Can the mods at a poll, completely forgot that part?