I think Bon Jovi the band requires both Jon and Richie. The two of them have created their sound. i like both of their solo stuff, but have to say I think Jon would have "made it" no matter what, he has that "it" factor. Richies good, great even but I don't really see him as a successful frontman. I don't know how long either of them would have stayed in it without the other though, I've always thought they had complimentary character traits. I think they keep each other grounded and they feed off each others energy and ideas.