Westbrook and Rose have always been vastly overrated (especially Westbrook ... seriously, he is a terrible shooter AND a terrible passer. He is just super athletic). Neither should be in the discussion for best point guard, quite frankly.
Honestly, I think it is a bit of a wash between Chris Paul and Rondo, with D-Will just a notch below them. Chris Paul is consistently better than Rondo when it comes to scoring and not turning the ball over ... however, Rondo has more frequently shown the ability to come up big, and is generally a better passer. Deron Williams has a butload of talent, and he is big ... but he hasn't shown the ability to really lead a team in the way Paul and Rondo have.
Also, not only is this subjectively true, but the advanced stats back it up, too. Paul, Rondo, and D-Will are higher in almost every metric than Rose and Westbrook, the only exception being PER (which is a terrible metric that pretty much only measures scoring).