I think ALOT the dislike for Hillary comes from the massive hitjob that Trump laid on her. He outright called her a crook, a liar and that she needed to go to prison and he got away with all that shit with a ton of people believing all of it. I don't think Cruz or Jeb would've been able to do the same thing and gotten away with it, but Trump being Trump completely got away with it with no problem.
I really believe that if Hillary ran against a Cruz or Jeb Bush, she wouldn't be nearly as disliked as she is now thanks to Trump not giving a fuck and going 100% dirty on her with the accusations and name calling.