John Thune, perhaps? Just kidding, he's not going to run no matter how badly some people want him to...
Clinton has no charisma, and people seem to think she's unbeatable, so it's possible. Same goes for Bush, Walker, Sanders, Cruz, Paul, and some of the others. 2016 will probably have a good mix of charismatic and qualified candidates. I give the edge to the experience over charisma.
Clinton has some charisma, I guess more than Cruz.
??
As much as I dislike the man, Cruz is a fantastic speaker and debater. I remember watching him at the 2012 convention and coming away very impressed (I didn't know who he was at that point). He was the top debater in the country in his youth and as a job convinced others with his oratory. Hilary in comparison is boring and stiff, and lacks the fire of a Cruz.