You're forgetting a key issue here. Great point guards make the players surrounding them much, much better. Which means that if it's apparent your point guard is the best player on your team, your team is actually crap. Would David West have been an all-star without Chris Paul? hahah yeah right
If you have a great point guard on your team, he should in fact APPEAR to be the second or third best player on the team, since his purpose after all is to elevate the other players around him.
Chris Paul has a crappy team. Jason Kidd had a terrible team on the Nets and he still took them far. The Suns can't play defense to save their lives, so of course they won't win anything (and Steve Nash was overrated as a point guard even in his prime). So it's not fair to judge these incomplete teams.
To see a better comparison, look at what happened when Mo Willliams went to the Cavaliers. Or look at what happened when Chauncey went to the Nuggets! Mo Williams, who was barely an all-star point guard, was still enough to turn the Cavs into a lock for the NBA finals. Chauncey, who for some strange reason isn't touted as the top 5 point guard he definitely is, turned the Nuggets around completely and now they have a chance to win a title.
How is Chauncey to Denver any less impactful than, say, Gasol to the Lakers? By your argument (that great point guards are less important), the Denver-Pistons trade shouldn't have done much of anything. Not only was it an upgrade at the point guard position, but it was a direct swap for another all-star point guard in Allen Iverson, thereby making it only a "slight" upgrade. Yet it transformed the team. If what you were saying was true, that superstar point guards don't really help your team, then try to explain Chauncey Billups.