Very diverse must see TV

So how is it that The Office is roughly the 50th highest rated show on television and Grey's Anatomy is the top show? The Office regularly offers comical delight, with tonight's episode featuring a marvelous press conference gone wrong in front of the best of Scranton, Pennsylvania's media. Grey's Anatomy regularly offers tense moments, with tonight's episode featuring some Amazon fish swimming up some guy's penis nearly killing him.

So again I ask, how in the world are these shows at opposite ends of the Top 50 television shows today?