You know; you're not going to like my answer, but i think *none* of them are best for you. If you'd like, of course you can be friends with them. But let me tell you why i don't think you should date any of them.
Guy #1 - you do NOT want to deal with someone who's Bipolar. You do NOT want to be in a relationship with someone who's Bipolar. Unless they are getting help, or are doing the right things to get help, i PROMISE you he will take you down with him; even though it's unintentional on his part. He will take away your life, your energy, your everything because of what he has to deal with. Trust me, i know from a LOT of unintentional experience. One moment, you're their everything and you feel so wonderful and loved. The next, you're absolute trash and are expendable to them. It will just destroy your mentality no matter how strong you think you are. He will hurt you mentally and physically. He will abuse you in all ways possible. i am telling you, you may think you know him, but you could not be more wrong.
Guy #2: If he's not going to break up with the girl he's already going out with, do you think he's going to truly pursue a relationship with you? If he truly loved you, he'd break up with the girl he's dating and go out with you. When he says he loves you, he might mean it in a different way. There are many different meanings to love; more than just the way you might be thinking of.
Guy #3: If he's not patient enough to be there for you and listen to you, no matter what might be on your mind and what you want to talk to him about, do you really think that's boyfriend material? Do you want someone to ignore you when you need someone to go to / to talk to?
Out of them all, i would say keep the closest friendship with Guy# 2. He sounds the most normal. Even though he's in a relationship, doesn't mean you can't be good friends with him. The other two guys i would say get over. The Bipolar guy, even as a friend, is going to end up hurting you. The other guy who gets mad at some of the things you tell him, in my opinion, isn't even good enough to be a friend.
Don't fret though...don't give up. You sound like a great person, there is a great person out there for you. You just have to look in the right places.