if a game has high sales it means it is a very fun game for many people. same with all these blockbuster movies. you could say fun means quality but i think that is another kind of quality and not really what people consider as quality when they review a game or movie. it's more the "good if you come back from work and just want to have some stupid fun without really thinking about what you play or see" effect which makes many games and movies so successful even if they are way behind others in stuff like storytelling.
hope you have a clue what i mean.