I like this guy but he has a girlfriend?

Let him be and look somewhere else. If his relationship is working out fine, and you're telling him that you like him a lot, then things might take an awkward turn.

I would probably not tell him. Just be brave and try to fall out of love. He's taken and it would be wrong to harm that relationship because it would be selfish. It would likely cause him a lot of pain and confusion if he ends up having to choose between her and you. It could also lead to a lot of guilt for you if you end up being the cause of their breakup. I wouldn't want to be the girlfriend in a situation like that, so I would avoid doing it to any other girl. I know it hurts a lot to have to remain silent, but it would probably be for the best.

Well. tell him you like him, and let him make a decision. If he wants to break up with her for you, he has the opportunity to. But if he doesn't, just continue to be friends and find someone else to like, for now at least- while he still has a girlfriend! As long as he knows you like him, it's in his hands to decide what he wants.

Dont you hate it when that happens but there really isnt anything you can do about it,you can tell him that you like him but that's not really gonna make a difference since he's been with this girl forever it might make things a little awkward.But I say to try to look for someone who's not taken and that will share those same feeling with you don't mess up the friendship you and that one guy have.Time will tell but don't wait for him to break-up with her because its a waste of time and you got to see the other guys around you good luck.!