I am not saying those people are bad candidates (none of them beside ryan are batshit crazy, and ryan isn't crazy he is just a conservative hedgehog) but all four of them are yawners, in much the same way Romney was a yawner.
I do agree in that I find Paul Ryan a total snoozer, a very unattractive candidate for an independent such as myself. But I disagree on the other three. Maybe a good 3 or 4 years ago I would not have given Christie a second thought but I actually find him impressive although I do think he needs to work on being a bit more tactful when responding to criticism. I like Rubio and he might not be all flash and "exciting" in the way you want but the man is smart. I like what he has to say and I like how he says it. I would most definitely consider voting for him. As for Jeb Bush, he is probably the Bush that should have become Bush II, not is dim-witted brother. I have read interviews and I frankly like quite a bit of what he has to say. But, I think his downfall would be that no matter how smart of a man he is or how good of a candidate for the position, many Americans would be very hesitant to vote for another Bush. And I don't mean because he's a Bush but rather the same reason I think Hillary Clinton has no chance - do we really need another four years of one of two families that were in the White House for a combined 20 years?
-Brandon Sanderson, The Way of Kings