We all look and no it's not bad. It's an instinct. Plus it's fun to look at the art of the human form. To hide this will just drive you nuts. To hide yourself from the world in certain ways will just frustrate you.
A girl recently posted on yahoo questions about this. She asked if it was bad if her bf told her that her friends or other girls were hot. The answer is no it's not wrong. Sure it may hurt her feelings but only if she is insecure. To be secure about your feelings with another is important for relationships. A woman should be able to express her likes and dislikes in whatever gender she prefers with her mate. A man should also be able to do this.
By expressing those things it doesn't indicate that we like others and the one being told. It just means we like what we see. At least he was being honest. It is interesting to see what the other sex likes anyhow. Why hide it? If you like it why not say something. Be confident in what you like and be confident in who you are as we all are different and are bound to like different or similar things. Enjoy this life you are enabled to live.
I look, we all look. Yes even you women look. Don't lie to us men, we know the truth. If you aren't secure with what your mate says about others or you then you may just need to work on your own self image. You must be able to love yourself before others can. That and you are not supposed to be what others want all the time. You are your own person.
Enjoy this life as it is a gift to exist and a gift to have the free will to reign your life as much as you possibly can without ruining someone else's existence. Well you can but that's just not nice.