Duncan would not get the Jordan comparison because of how Jordan dominated during his 6 championships run. It was not only a statistically dominating 6 runs, but they were back-to-back-to-back two times. The last two Spurs les found the Finals MVP with a Duncan teammate. And in the midst of Pop turning over the focus of the Spurs offense to the perimeter guys and three point shooting, while Duncan has still been vitally important to the team's success, there is at least the perception that Duncan was more of a secondary player on offense. A 6th le would require not only Duncan winning the Finals MVP but also return to the 23+ ppg scorer he was earlier on in his career, which is unlikely considering how the current Spurs offense is built. And even then, I don't think he gets a Jordan comparison. He's already in the conversation as one of the greatest winners in NBA history. But when you also factor individual dominance to go along with those championships, I don't think Duncan can get involved with Jordan.
Right or wrong, Parker and Kawhi taking home those FMVPs have limited the opportunity for Duncan to get involved in such a Jordan comparison.
I think Duncan and Shaq are close personally, with Duncan obviously having more consistent and sustained success and Shaq with more dominating le runs (and more dominating career in their early years and prime years). Both have 3 FMVPs. A 6th overall le probably does help Duncan edge Shaq.