In Lord of the Flies, Ralph should have been the leader from the beginning, because he had the strongest leadership qualities. Ultimately, it doesn't matter who the leader was, because the point the book was making was to show that society would break down without laws, no matter who the people in society are, even people as clean as British school boys.
Ralph should have been the leader from the beginning, otherwise the novel would have turned out differently. It was Ralph's decisions that led to Jack's ability to form the rival group. Without the rival groups, the plot of the novel is lost entirely. Jack wouldn't have fared any better because there was antagonism between the two boys from the beginning.
Jack was the one who made sure they were all fed. Sure he was a butt, and i wouldn't trust him with my kid, but he was the sole reason the kids got off the island alive. If it were not for him the kids would probably be even more violent due to starvation.
He got all the kids to join him. Sure he was a butt, but he knew what to do and how to do it. He is the only reason the kids were alive to be rescued. If it were not for him they would have died or gone mad hungry.