It's fun to be liked and there is the thrill of starting something "new" but this is doubtful to workout for you. Your bf sounds like he cares a lot and you care a lot for him. This other guy only seems to notice you when you are around and at that seems like he is more interested in sex than anything else. I would try to step back and look at things objectively and decide what you really want.

On paper, starting a relationship with a guy that has a gf of 2 years and leaving a relationship to do it doesn't sound like a good foundation for anything lasting.

If it is just about sex then that could probably happen but I doubt it would lead much beyond that.