smartest witch of her generation

I get irritated when people call Hermione the brightest witch of her year because it’s obviously such a bias opinion. How many 14 year olds has Sirius met? And people will take that quote from a man who just escaped prison and was tortured for twelve years and act like it’s a fact that Hermione is the smartest witch of her generation when we haven’t even met a large majority of her generation.