First and foremost,I don't think Bobby would want the job. He had a decent life,no aggravation,and was happy to stay put. Having said that,I don't see Bobby as holding on to the top spot if he were to get it. No question he was loyal and a good earner,a good husband and father,and one of the most mentally stable guys in the Family,but not Boss material.
Bobby had a soft side,and was a decent human being,and these things,while admirable in our world,are considered birth defects in the OC world. I know that Bobby did commit some violent acts,but I feel that it was only because of orders,and if it were up to him,he wouldn't have.
Bottom line,I think that he would have been perceived as weak both inside and outside the Family. New York would give him the illusion of respect,but would have him dancing on puppet strings,and his own guys would probably get away with chiseling him on their kick-ups way more than they would have under Tony.
Good earner,great guy,bad Boss.