I am not sure if this question is referring to American football or European football, which are two completely different sports. If you are referring to American football, the most exciting player to watch has to be Tom Brad of the New England Patriots. He is lauded by many as one of the best quarterbacks to ever play the game.
He is extremely competitive and is known to turn the game around even in the face of almost certain defeat. If you are referring to European football, the most exciting player to watch is Cristiano Ronaldo of Real Madrid. He is one of the best players alive at the moment.