Continue to teach by example. Live your life showing him good sportsmanship, empathy for others, and the value of a strong effort (emphasizing effort and not result as the measure of performance). Comment whenever appropriate to verbally reinforce these values you are living. He's still not too old to be read to; ask your children's librarian for books that deal with your concerns. Also check out any of Alfie Kohn's books on non-competitive games for kids.
Ask him if he would like to help a child he knows become more skilled at something (sports, academics, etc.) he is good at. Sometimes kids become more sensitive to others when they help those less talented than themselves. There will also be a natural series of life events that will dictate the impossibility of your son's demand to be first/best. You'll be there to put it all into perspective when he falls.