I guess the same applies to girls as well. I don't think it is a "guy" thing.
However, a clear distinction should be made between "liking" or "finding somebody attractive" physically and "falling in love" as some of the answers here pointed to. To like someone's physique is similar to having one's favorites when it comes to food, ways of dressing, likes in literary genres, movies, music and lifestyles, etc... To fall in love is not always directly associated with looks though it might be sometimes. One usually loves somebody because they have a number of qualities: looks maybe one of these but it is not the most important one. I think that not a few relationships quickly "bite the dust" because they only relied on appearance. True love is much deeper than that and to survive it needs to consider all of the qualities one's partner has, not only his/her physique.