I have found that "best buddies" and "good manager" are not always correlated. That is to say, sometimes having a good personal relationship with a manager is a sign of a good manager and sometimes not; one does not imply the other.

On the one hand, being good friends with a manager may prompt one to go the extra mile because you're helping your dear friend (and perhaps vice versa). On the other hand, a deep friendship may cause you to ignore or downplay flaws or problems (that may seriously impact the customer, etc).