I personally think age is a major factor here.
Everyone IS attractive in their own ways - and every individual has his / her own personality trait that sets them apart from the rest.
Ok - I may be a little bit stereotypical here... but the younger generation more often than not place more emphasis on physical attributes. How often have we heard people muse: "Oh... when I was younger, I would find him/her attractive - but he/she's hardly my type now." It is not uncommon to find that the idea of "beauty" that teens have would be entirely superficial; fueled by the idealistic images portrayed by glossy magazines, movies and glamorous models. This does not apply to all, though... I have come across many young people who know precisely what they want, are able to think beyond their years and put many adults to shame.
Most prepubescent teens would get excited at a walking, breathing 'run of the mill' sexy person as immortalised by their idols and the faces staring at them from the pages of a magazine... but as they enter adulthood, most will find that their preferences grow with them. To put it crudely, it's no longer enough to have "Wham, Bam, Thank you ma'am(s)" sessions - the ability to communicate with the other person would feature more.
When a person appeals to you - either through intellect or their little quirks and idiosyncrasies - they become instantly attractive to you.
Of course it would be hypocritical of me if I said that looks does not matter... for a spark of interest to be ignited in a person, there must be that certain something about another person that appeals to the eye.
Having said that, it's been proven that we are societal and communal creatures. As much as we would like to disagree, society DOES play a part in what we (as a whole) consider beauty. There have been many studies by sociologists, (Desmond Morris, Dr. Stephen Hawking), that have shown societies' major influence on our "concept" of beauty. For example, there is a tribe in which the women stretch their lips and wear bigger and bigger "lip plates". Many western cultures find this unattractive and even revolting, but to the members of that tribe it is a mark of sheer beauty, and we are the "ugly" ones.
Hollywood, with it's pervasive print, television and movies, sets the tone for a lot of cultural definitions of beauty in many Western countries... and lately, the Asian one, too. Recent studies have shown that many people all over the world are adhering to the Hollywood 'standards' of beauty... which has led to an alarming increase in illnesses such as anorexia and bulimia in countries like the Netherlands, Belgium, France, and even the UK.
Society determines, to a very large extent, its version of beauty. However, I do believe that each person is a unique individual with their own unique characteristics. The question is
when they find their own personalities. So... just because studies have shown that we react in a more positive way towards what the
current idea of beauty is... there is plenty of room for individual interpretation.
To each his own - one man's meat, may be another man's poison.