What is a good sound in your opinion?
The facetious answer is 'probably not the same as yours.' Not much help though I guess. The truth is though that I tend to listen for different aspects of a sound which a comparative novice might not. By novice I mean someone not having 33 years of experience to draw on. Most of those experiences have been good. Some have been dreadful and quite a few have been in between.
The point is that what I might consider to be a good sound really isn't important. My job is to help the buyer get them the sound that brings out the biggest grin on their face, the greatest leap in their stomach, the biggest pounding of the heart. All the rest is irrelevant.