Basically what jamie1 said, you can like girls clothes without being a sissy. perhaps you just have a desire to cross dress? Or maybe it honestly is just that you like the way they look. People put too much emphasis on what is boy and girl clothing. While dresses are primarily girls clothing in the western world, in some parts of the eastern world dresses can be considered men's clothing as well.
So in my opinion: No it doesn't make you a sissy. But you may have an interest in cross dressing, or perhaps its a feeling of rebellion, knowing that its something that guys normally aren't suppose to do, wear dresses and like pink so on and so forth. The brain is wired to want things its denied.