First, he leads you on and acts like you two really have a lot of potential for a relationship, and then turns around and tells you that he's also liked someone else the whole time and that he'd rather be with her. It's one thing to like another person, but in my opinion you shouldn't be leading someone else on while you feel that way.

Now, it seems like he's not really into it once again. He's just playing around with your feelings with no regard for how all of this is affecting you. By completing blowing you off after you put yourself out there and asked him out, he's showing (once again) that he would rather see what else is out there before he commits to anything.

Again, this doesn't make him a bad person but it shows that maybe he isn't mature enough for a relationship yet. If he can't make any commitments to people that he has feelings for, maybe it's best to just let him figure out what he really wants before starting something.

At this point it's completely up to you, but my advice is to not force him into anything. If he's not ready for a relationship, then there isn't much you can do besides accept that and move on.

If he does end up turning around and deciding that he wants something more, then go for it. However make sure that you are both prepared to commit to the relationship.