My 13 year old son is EXACTLY the same....I could have written your post myself. I have one older son and one younger daughter. I'm considering getting professional help because I don't want my daughter to pick up his terrible attitude. He's an "A" student so we know he's smart enough to know better....it's like he can't control himself. Good luck!
You will likely not be very influential in changing this negative and self-centered attitude. Your son will reject what you have to say. Perhaps the best influence you can provide is to model reasonable, altruistic behavior, and know that this will have some beneficial impact. In the meantime, consider who in your son's life might be able to make a dent in his way of thinking and acting. Sometimes a friend or a relative can be more helpful than a parent, simply because the outside-of-the-family person is not regarded in the same way as the parent is. You might also run this situation by a mental health professional who is experienced dealing with adolescents. Such a person can offer you some guidance in how to handle the situation in the family. Finally, consider the possibility that your son may need some help himself - describe him to the clinician you consult, and see if an evaluation is recommended. Sometimes, but not always, such children are displaying the impact of a mood disorder, and such conditions can be treated.