You need to tell him how you feel, but you can't force him into liking you, if he likes the other girl, then you really can't do anything about it, Sadly..but you can tell him how you feel. If you don't want to lose him, don't date him, it'll your friend ship up, and everything else up, so just stay good friends with him, that's better than nothing it really is, I understand where your coming from, too...so just remember, tell him how you feel and leave it at that. you never know..he might come around some day, just maybe not today <3 (:

Tell both of them you know that you are friends, but that you don't want to listen to them talk about eachother because it hurts you to have to hear it. They should respect that.
Would you two dating really ruin the friendship? If you two broke up, things between the both of you would really never be the same at all. Do YOU want to risk losing that? It sounds like he doesn't.. Maybe you two could set up a date to go out and just hang out, like out to eat or the movies and see if dating is something that would work for the two of you or if yall are better off as friends even though it hurts you.
I hope everything works out for the better and you feel better about the two of you, too!