It's absurd to think Popovich, Ginobili, or Parker were only great because of Duncan. The great players that Duncan played with all had significant success apart from Duncan.

Does David Robinson get credit for Duncan because Robinson was a great leader? What about all the other players in the NBA who have been known for being great leaders? How much credit should they get for their leadership compared to Duncan when you are comparing all-time top players? Could Duncan's leadership style worked as well if he had been part of organization that didn't have the stability the Spurs did? What if Ginobili wasn't willing to play the role he did and demanded a trade? Could Duncan's leadership style have worked as well in a market like New York or LA?

If I'm comparing Duncan and Garnett, how would Duncan have handled all the bad seasons/rosters that Garnett had to deal with when he came into the league? How would Garnett's career had been if he had David Robinson as a teammate/mentor when he came into the league? What if Garnett had a coach as good as Popovich and teammates as good as Robinson, Parker, Ginobili for his prime years?

So I absolutely agree that Duncan had great leadership skills, but there is too much subjectivity and too many hypotheticals in my view to base all-time player rankings on "leadership" skills.