Depends on the person.
If you have a warmer complexion, (olive skin, exotic maybe look to you)
and you're a natural brunette, and you naturally HAVE brown eyes, then yes, they will probably fit your features and look attractive.
Eye color is subjective in terms of attractiveness, it varies on the individual.
When I see people with lighter complexions, on Arian decent typically, (blonde hair, rosier complexion), blue eyes look best of them, and that is because in most cases, a natural blonde will have light eyes, like blue.
That is why whenever I see a person wearing colored contacts, it looks so fake and unattractive.
Sport what god gave you, that is the most beautiful for YOU, individually.
Also, to answer your question specifically, it is probably because blue eyes, unfortunately, are more rare and less common than their brown eyed counterparts.
Blue eyes stand out more in a sense because less of the population has blue eyes.
But, that doesn't mean you are not an attractive person or that you are NOT beautiful, eye color can make a person stand out..
but eye color alone doesn't justify ALL AROUND on whether or not you are deemed attractive or beautiful, that is ridiculous.