The girls attract boys. So they appear beautiful to boys. A girl does not consider another girl beautiful. A girl is attracted towards boys, whom she may consider handsome or a beautiful boy. Tulsidas has written- Naari na bhaye naari ka roopa- A woman does not like beauty of another woman.
I think beauty is a psychological approach.What I feel beautiful may not be thing of beauty to others.For all men girls will not be beauty queens.
But "a thing of beauty is a joy for ever"
There are lot more beautiful things than girls but yes as a human being its natural for all boys to get attracted towards girls and I am sure girls get attracted towards handsome boys too. So its a give and take offer.