If shyt hits the fan that's the person on the front line defending the village. The 3rd, 4th, and 5th were all arguably the strongest although the 5th got surpasses by Naruto during her reign she was stronger than him when appointed. He'll the 1st and 2nd were too.Being Hokage doesn't mean being the strongest. Kakashi & Shikamaru were both said to be hokage material by a few people in the manga.
And I didn't realize that Sasuke was crying in the last panel