I don't like the term "retired," it should really be split into two: trashed and on hold.
I personally group my library by my desire to play:
- probably never - essentially trash
- replay - games I enjoyed and intend to revisit
- done - games I enjoyed and have no intent to revisit
So for me, "retired" could be any of those three. I don't always "finish" games (credits roll, 100% complete, etc), so the label doesn't really say much about the quality of the game or whether people enjoyed it, just that they decided to set it aside for whatever reason.