He was the 1st Hokage for a reason
and the fourth became the Hokage because he was compared to the other Hokages to see if he was good enough, so he either has to be as good as, or better than, the first, second, and DEFINATLY the third, because he took the thirds job from him while he was still alive, and since Kishi said that the third (in his prime) was the strongest, and the fourth was good enough to take the thirds job while he was living, that tells you something about relative power, doesn't it?