Namor can hang but anyone on the opposing team can beat him for a healthy majority. Black Bolt is powerful but he isn't physically on anyone's level here (even though he can hang for a bit). He also will not start straight off with the scream and with the basic knowledge rule that is in place, the opposing team would try to take BB out ASAP and all of them have the tools to do it. With that said, this fight is a mismatch and Superman team wins every time after a hard fight.