Yes, women in the clergy can be successful. Women that are in the ministry and hold high beliefs in it can be successful in any form of ministry that they believe in. I think hat many women today take on this role and do very well. So yes they can.
Women possess characteristic traits that would contribute to their success as clergy. Women are sympathetic and are great listeners which would allow them to relate to their congregation and connect on a more personal level. This connection and ability to relate would endear them to their congregants and contribute to their success in the ministry.
Women have succeeded in every new field that they have entered. There is no reason to think that the clergy will be any different. Though there is bound to be some resistance within their own flock, there was also resistance to women entering the fields of medicine, law, the military, etc. Once the initial shock is overcome, it will be clear that women are just as capable in the clergy as they are in other fields.
Yes, women in the clergy can be successful. However, women in the clergy have to have the support of the specific church or religious group to which they belong - otherwise it will cause fracture and division within the religious group. In many forward thinking religious groups, women are treated as equals with men and have no problem.