How do I choose between two guys?

I have been with a guy for 4 years, he's a great guy and we also have a son together. The problem is that I'm in love with a guy that I've been talking to for about 2 years but I've never met him in person. Honestly I'm bored with the relationship I have with the first guy and he makes want to go after the second guy, I don't know how to tell him that. What should I do?