I've known him for a good year and a half, and about four months ago we found out we live only about two blocks away from each other and started hanging out all the time.
At first it was awesome, for me at least a total click at least in the friendship department, I can tell him anything, and unlike other friends, even girlfriends, he gives me honest advice, and I like the way I am around him.
Since becoming close to him I've discovered how to actually like myself properly, and I feel like I've become a better person.
Now the problems really started when I began to realize that I might like him, at first I was more concerned with our friendship, because not only does it mean the world to me, but he has also told me on many occasions that it means a lot to him too.
Then one day I was talking about him to a friend of mine and she mentioned that the way I spoke about him and look on my face made me seem like I was in love with him, at first I denied it entirely but then realized she was right, and I'm not one to cry but I started to cry when I realized this.
He is the first person I have ever been in love with, and I didn't want to make a move because I knew something like this could get really bad really quickly.
It was about two weeks ago that while we were talking about relationships he mentioned my girlfriend as being the best choice to date currently, because he saw the best future with her.
It hurt to hear, but other then that he didn't really say anything further about it, but then the very next day we found out that another one of our friends was planning on asking her out, and he said that he was actually planning on asking her out too.
I was crushed, but not wanting to add my feelings into this already complex mix, I've continued playing the role of best friend, and have even been helping him.
The weird part is that he pretty much treats us the same way, I mean we stays up until 2 in the morning some days at my place just talking, and never seem to run out of things to say, or just the other day, even though he had ridden his bike he walked me pretty much the whole way home even though it was in the opposite direction.
The big thing that's really killing me is that I know him and I are closer then he and her are, and from what I can tell he doesn't know that much about her, and she doesn't know that much about him either, and I don't know if she actually likes him, or if she just sees him as handsome and might be a good idea to try and date.
This whole thing is just absolutely killing me, because on one end I want to be selfish and tell him how much I like him, but then on the other end I just want the both of them to be happy, and I'm afraid of losing both of them.

Maybe you should let it goes by try to focus to something else? I mean if your dream guy likes your best friend at the first sign then what can you do with that, feeling is very difficult to understand and this is not easy to tell him that you are in love with him after he told you that he likes your friend and want to be with her. You might say it before, right? well, you think it might be too late but you still want him. I think this is just a very new feeling that you even didn't realized yet before, when you feel you are going to loose something that you already have for a long time, it's not different than an old chair which inside your room for a long time and you even don't feel how much you like it, but if someone going to take it out then you feel you still want to have it. I don't know about your real feeling, but with my experienced, this is just a transient feeling at the beginning of life. You will have more new friends and find a nice guy that love you at the first sign as well. So don't wasting your time to wait until you see their relationship is work well or not and then you will be the one who face to face to fix all of the problem after that. I think if their relationship going well, then you won't have chance to be with him, but if his relationship go down and broken then you will come into it, for a chance? After you knew how many happy days they spent together? C'mon. Find another one, there are too many nice guy in the world and time will fix your hurtness. This is very easy to fix because your pain is not like someone who ALREADY love you now going to love someone else. This is just at the beginning, forget it, man is part of your life, not your life, so let be happy, there are so many interesting men awaiting for nice girls. Life never stop :) ( My English is not the best but I hope you still understand what I mean) :D

You need to talk to him and tell him how you feel, then allow him to make the choice he wants. He might be feeling the same way, who knows?

I think you back up and stop wrapping up so much time with your best friend. Give others a chance to be friends.

How old are you both?

I'm in the same situation. I'm even giving him advice on how to win her over. But he makes me feel something I've never felt before. The ways his eye sparkle when he smiles, and the smell of his cologne, the way he laughs silently, how he can just get so deep when he is with me, and the way that he stuck up for me when no one else did just makes me fall deeper into his spell. I feel trapped; like I can't even control my own thoughts anymore. He has stolen my heart and won't give it back. I just go along his love for her, even though I know that she will never like him considering the fact she is dating someone else. I feel bad that I feel so jittery all the time and that I get so excited to see him and talk to him. Is that all my life is based on right now? A stupid boy that I fell for? So what I recommend is this:

A. you tell him the truth about what your feeling. If you can share anything because your that good of friends then you should be able to tell him this. And explain that's if he doesn't feel the same about you that it's okay and that your friendship shouldn't change. Yes that is a big leap

B. You concentrate on something else. Like school, sports, friends, etc. Even look for a different man for you. Maybe you just weren't meant for each other and you were just supposed to be friends. Who knows?

C. You remain the good friend you are and back him up on his opinions. Yes it hurts and is hard but you were his friend first and according to what I've heard he sees you as a friend now and he needs you more than ever. Keep things the way they are, If their relationship isn't that solid then hey maybe they will end soon enough. Your time will come.

Honestly I think you just need to go with that gut feeling and do what you feel is right. None of these answers will decide for you and help you learn new lessons in life. I wish you the best :)