I've been cheated on once...and I know it would bother me if my gf was hanging out with another guy more than me. So I'm a bit biased on this subject.
I believe there are boundaries to a relationship. Sure you can be friends with the guy, but I feel that your boyfriend should be the one and only guy you share your deep secrets and spend most of your time with. I agree that if you want to spend more time with him, date him not me. It sounds jealous, but I'm thinking logically as well. I mean don't put someone in a situation that's going to make the other feel uncomfortable.
As a guy, if I had a girlfriend, I wouldn't be hanging out with other girls more than my girlfriend.
Ohh well...that's just me.