It depends on your definition of transcendent.
...which is a label you grant as a badge of achievement after a player has won it all as the best player on his team. Nobody would call Carmelo (or Fat Lever) transcendent at this point.
If you want to know why there are more transcendent big men than point guards, it's simple math. You're comparing all the players at two positions to all the players at 1 position. Are there more transcendent bigs than transcendent guards? Probably not. Are there more transcendent bigs than transcendent wings? Doubtful. Are there more transcendent players at any 2 positions than any single position? Yes.
Well, thank you for the math lesson, Tim, but I was aware of that fact. However, the number of "transcendent" big men exceeds the point guards by a far higher ratio than just 2:1.
As for the fact that there are fewer tall players than smaller players? The nba is somewhat height based, meaning that the taller you are, the bigger your impact for a given skill level. If Bradley and Vitor are equally skilled players then Vitor will have more of an impact on a game. If Rondo was the exact player he is but the size of a center he'd be the best player in the history of the game.
So you would agree that under a salary cap you´d get more bang for your buck if you pay $20 million to a good Center instead of a good PG?
Consequently, wouldn´t you also agree that one main advantage of investing in quality big men lies in the fact, that, 5-on-5, you´re winning a more important match-up in any given game?
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Generally, I believe the rule changes allowed PGs who formerly would have been considered mediocre at best to look like stars. However, the number of potentially "transcendent" PGs is roughly the same it has always been. Quality is still quality.
In effect, from a team-building perspective, PG has become even more of a "throwaway position", on which production can be much more easily replaced than on any other position.
As for the OP, I would say that in an ideal world, not only scoring point guards, but point guards in general have become somewhat obsolete and are replaced by a third wing who can defend and play off-the-ball, while the ball can be in the hands of your best scorer/ball-handling wing. In my opinion, the teams you listed were somewhat desperate (not that I blame them), and simply took their best chance of getting into the play-offs.