The hokage and the sannin are about the same level in power. Example jirraya and orochimaru are sannin's. There are only three sannins which were taught by the 3rd hokage and are recognozed by the whole naruto world. There is about class sennins. People tend to mix up the sannins and the sennins. The sennins are a bunch of legendary ninja's that has an giantic amount of power, however they are no match with the sannins.