Thanks for the article
Ferrer's stat is also higher because he plays more on clay.
Also for him and Davydenko, they play more smaller tournaments where it's easier to raise that stat (like all of the stats made in %wins by the way
I do think that Djokovic is the current best returner (the stats cover a very large period since 2006 but since last year Djokovic improved a lot that part and I think he had the best stats for that last year), but Ferrer is clearly one of the best ones : I saw him return Ljubicic's serve damn well, which few players can do, also Raonic in Melbourne this year.
As for Davydenko, what's strange is that I saw that he doesn't perform very well against big servers quite often. It seems he doesn't like kicked serves especially.
Something else : stats don't always show it (because winning points on second serve can be made by something else than the return) but the abilities on return on first serve and second serve are two very different topics imo : on first serve your anticipation and eye are tested and you mostly try to "return in the court" first, on second serve the best players manage to be aggressive but the eye is less important.
For instance Berdych to me looks bad to return first serve but quite good at returning second serve. Ferrer is good for both.
Federer is good at returning first serves but doesn't have a very good ability to attack second serves (where most of the time players look for his backhand)