My son just loves football.  He plays for his high school team. Football ranks among the most popular sports
My oldest son has also played football for an elementary team. How have you managed to keep him motivated to play?
He needs no motivation. He loves football and watches it all the time. He is forever telling me the rules - about the offense and attempts to advance down the field!! 
That is great. He must be exciting to watch and fun to be around. I hope he continues his passion for it.
fingers crossed.  It is good exercise and they learn great teamwork with the scrimmage, passes and techniques.
The bonds he creates with his teammates are surely made to last. There is a lot to be learned from football, including conduct that relates to real life. 
Very true. Following rules and guidelines and also being in control will help them in life.  Also learning rules like about end zones, goal lines, sideline and out of bound rules teaches them so much