What conclusion does Ralph come to about being a chief? What about his own ability?

In Chapter 5 of "Lord of the Flies" Ralph paces along the water and is

overcome with astonishment....understanding the wearisomeness of this life, where every path was an improvisation...

Ralph recognizes the need for someone with experience to guide the boys.  As he faces the chief's seat, Ralph decides that he cannot think as well as the adult-looking Piggy who "could go step by step inside that fat head of his, only Piggy was no chief."

Later, during the meeting that Ralph calls to impress upon the boys the urgency of keeping the fire going, he holds the attention of the group as the boys are aware of the missed rescue and fear Ralph's anger.  But,he starts to lose their attention as he speaks too long.  Only when he again becomes angry does he regain their attention.  Jack is subsequently able to wrest this attention away from Ralph by playing upon the boys' fear of "the beast."  Ralph realizes that his advantage is lost, at least for the time.  He refuses to blow the conch, telling Piggy," If I blow the conch and they don't come, then we've had it...We'll be like animals.  We' ll never be rescued."  To this Piggy retorts, "If you don't blow, we'll soon be animals anyway."

Without adult supervision, adults who have more experience than Piggy and can think better than he, the boys are incapable of ruling themselves for long, Ralph realizes. At the end of the novel, this poignant realization causes Ralph to weep for the end of youthful innoncence and for the "darkness of man's heart" that triumphed over both Piggy and him.