Everybody compares themselves to other people and have been doing this since they were a child. It is a natural thing for people to do because it provides a frame of reference for who they are and where they are in life.
The problem is that most comparisons are negative and based on insecurities and fear. This can lead to a person becoming very bitter about another individual and even angry. Negative comparisons like these often damage a person's self worth because they believe that they are not good enough.