Duncan has a arguable case to be a top 5 NBA player of all time, probably 5-10 somewhere though. He's the best PF of all time imo. Kobe's probably just outside the top 10.
And pretty much every major publication has them ranked as such. Every one of the "greatest ever" lists has Duncan ahead of Kobe. And they're right. Duncan did everything right. When he was the best, he was the best. When he wasn't the best, he was willing to take a step back (and less money) to keep fielding a contending team. And he still has all the accolades (actually more) and championships beside his name.