Point is, either "position defining" player comparison is, in itself, incomplete until a championship is produced. And with Durant we won't know that for at least, I say, 3 or 4 years... because that's how long it will take the Celtics (er, NBA draft lottery winner) to: a) Fire Doc Rivers (the coach), b) fire Danny Ainge (the president), c) re-build a team and d) succeed with Durant in the middle of the team's new system. I argue the biggest piece of that puzzle is not drafting Durant, but actually the drafting/trading/free agent signings around him.
Remember, great players are defined by championships- Shaq/Kobe/Wade, Duncan/Robinson, Bird, Jordan, Magic in hoops. Brady, Montana, Elway and (gasp) Manning in football. And all of those superstars had a teammate or 2 to take some of the burden/pressure off their shoulders. Quick run-down:
- Kobe had Shaq
 - Shaq had D-Wade
 - Robinson had Duncan
 - Bird had McHale and Parrish
 - Jordan had Pippen
 - Magic had Kareem and Worthy
 - Brady had Vinatieri (and Belichick)
 - Montana had Craig and Rice and Taylor and Walsh and... (stop me at some point)
 - Elway had TD
 - Manning had Rhodes/Addai (and an inspired postseason defense that was invisible in the regular season)
 
Call it splitting hairs if you will, but I think that is a fine line that needs to be defined. No matter how great those non-champs were, and they were G-R-E-A-T, there is almost a societal class system that should be enforced between champs and also-rans.
Stats are nice (Marino, et al.). But it's all about the rings.
The jury should be out until then on Durant.