Despite being a completionist, I consider the game's end to be the canon story ending. Sometimes I'm so distracted by my "completionist mentality" that I completely avoid finishing the game until I've done everything else. But on the other hand, if I own a game, I tend to try to beat it at least once. The exception to this is my copy Thief which will not allow me to save past a certain point and so I've given up since I don't do speed runs.