I think it all depends on what kind and how much of the 'good' there was, don't you?
In my family I remember the bad, and not much of the good. I think that's because there really wasn't much good there - although it certainly wasn't ALL bad. My perception of the 'good' times in my family is mostly that they were simply moments in which the 'bad' was absent.There was *always* that feeling of walking on eggshells and the sense that 'not-bad' could suddenly erupt into 'bad' at any moment.
Maybe the 'ratio' at which one remembers good vs bad is reflective of how much of each there was.