Probably Naruto. I mean it's one of his dreams to become Hokage so Kishimoto-sensei will probably end the manga with him becoming hokage. The war can't last for that much longer and either Tsunade dies or she steps aside to let him take over.
Plus him still being a Genin has nothing to do with getting chosen as a Hokage. As long as they think you can handle it and would be the best choice to become a kage, then it doesn't matter if you're a Gennin, Chuunin or Jounin. And Naruto is only a Genin in rank; qua abilities and strengths he already long surpassed the rank of Genin.