A good PG is usually a good floor general, passer, defender, and rebounder.
For example, CP is arguably the best PG in the league; Rondo distributes a bit more than Paul while Paul shoots a bit more. Nash excels in passing and shooting but he is a defensive liability which reduces his overall impact on the court and team wins - that's one of the reasons why Nash is not ranked as top 5 PGs.
Additionally, the point guard position has evolved to where more of a focus is placed on shooting and scoring than ever before; therefore rebounding is another essential skill set to be looked at.