Djokovic is not 24/14 = 1.71 times better than Sampras, otherwise Djokovic would not be on lesser Slams than Sampras was on their 30th birthdays, whatever someone wins after 30th birthday depends on Great Age Shift + Strong/Weak next gens, so we can disregard that. Djokovic or Fedal are not better than Sampras,
Tier 1 : Big 3, Sampras, Borg
Tier 2 : Mcenroe, Lendl, Connors
Tier 3 : Agassi, Becker, Edberg, Wilander
Tier 4 : Sir Andrew Murray, Courier, Hewitt, Safin, Kuerten etc etc ... & Roddick too.
Tier 5 : 1 Slam Winners (not Roddick) who were not worth more than that....Medvedev is also in this tier, but I place Roddick above.
Tier 6 : Non Slam Winners who have other Big trophies and Slam Final s
Tier 7 : Non Slam Winners who are just in top 100 but average
Tier 8 ; Rest of the people outside the top 100