2. President Bartlet
Intelligent, charismatic, moralistic, an economics expert and a strong leader, who wouldn't want President Bartlet as their head of state? To think that Martin Sheen was only originally signed on to appear in four episodes doesn't bare to think about. Whilst each of the other characters are strong in their own way, President Bartlet is undoubtedly the standout of the show and the glue that holds the cast together. From his episode stealing entrance "I am the Lord your God, thou shalt worship no other god before me." Boy, those were the days, huh? to his final scene aboard Air Force 1, its difficult to imagine The West Wing being the success it was without President Bartlet. Whoever decided to make Martin Sheen part of the regular cast was a genius.