Sales numbers are not always indicative of a game's quality.

[jacks81x]

WereKitten said:

^

And btw: "people who don't look for much quality" is a very real case. Just as many DVDs are quickly grabbed from the shelves with the goal of keeping the kids busy while you have dinner with friends, there are games that are bought with no real regard for its quality. "I only want something the kids can play next friday at my daughter's birthday party" has been said to clerks all over the world uncountable times.

That's very true.  Parents buying video games for their children are the perfect example.  For the most part their objective is to buy games for their kids to keep them busy or as gifts during holidays and special occasions.  I highly doubt they do extensive research on the quality of the games they purchase.