well being in the same ninja team doesn't mean that they have to be close in strength. For example Sakura and Naruto/Sasuke are in the same team but their powers are very different. But yeah, Oro and Jiraiya should have almost the same power. We don't know how powerful Itachi is yet, but apparently he kicks ass. So I guess so far the most powerful is Jiraiya, although Hokage may have some kickass jutsus too.