Steve Rogers also know as Captain America is the leader of the Avengers because he is the first Avenger. He was a the first and most successful created super solider in the era of world war 2. He is a master of warfare. He has trained in every technique of martial arts. He has a strong sense of right and wrong. He is courageous, committed and honorable. His experience in World War 2 leading the Howling Commandos gives him the most knowledge to lead the Avengers. He protects the team and understands how to make the difficult decisions.