It's probably also important to note that Ralph didn't necessarily want his leadership role. He was given it simply by being the one to blow the conch in the first place. There are instances throughout the early part of the novel that suggest Ralph would much rather be one of the boys out playing instead of trying to play the part of the responsible person.
Ralph is charismatic and a natural leader. He is empathetic and observant and a problem-solver. For example, he tells the boys, "We can help them to find us. If a ship comes near the island they may not notice us. So we must make smoke on top of the mountain. We must make a fire." Ralph tries to assess problems intelligently and not emotionally, asking for example, "What was the sensible thing to do? " His friendliness and logic make him a natural choice to assume a leadership role.
For more on Ralph and other character's in Golding's novel, please visit the link below.