That's the question that Tyler Cowen asks over on Marginal Revolution asks. I was suprised to see this post, as I read Marginal Revolution because it's a fantastic economics blog... Tyler doesn't have any answers, but he does have provocative questions:
Can you imagine Bruce Bowen holding MJ to thirty points and Duncan going around Bill Cartwright at will? Could they keep the fast break of the Showtime Lakers in check, while exploiting the relatively weak defense of that team? How would they match up against the 1989-1990 "Bad Boy" Pistons, or the Celtics with Bill Walton?
Even though I'm a huge Spurs fan, I think they haven't yet proven themselves worthy of such consideration. They're playing terrific this year, but need to show consistency to be rated as highly as the classic "great teams." It'll take at least two championships (this year and, hopefully, next year) to make up for their collapse against the Lakers last year and take their place among the legends. Luckily, everything is in place for that to happen: their top players are signed for the future, and are young enough to either maintain their current abilities, or even improve. Of course, if next season isn't a full season, that will hurt their them in terms of their chances to prove themselves. Already one championship came in a lockout-shortened season.