Guilty about liking friend's boyfriend. Help?!?!?

First of all, telling someone your ual fantasies doesn't mean you're extremely close with one another. Second of all, there is no ring on anyone's finger in this situation, and if he truly cared about you the way you think and the way he describes, dumping his current girlfriend for you shouldn't be an issue. You have to do what is best for yourself in this world today, he just shouldn't be a jerk about it. If he simply tells her that it's not working out and he doesn't feel for her the way he feels for you, and that it is unfair to her for him being with her while having stronger feelings for you, then all should be well.