The NFL Network's top ten things that changed the game.
Best of the rest: college star Red Grange gave the league star status.
Best of the rest: Commissioner Pete Rozelle brought the league into the 20th century, negotiating television contracts, creating the Super Bowl, etc.
Best of the rest: fantasy football helped spur increased awareness of the sport.
10. Soccer style kickers helped boost scoring.
9. Bill Walsh's West Coast offense led to four Super Bowl wins, using high-percentage short passes to open up the running game and downfield passes. Walsh's assistants (Shanahan, Holmgren, etc.) spread throughout the league with similar offenses, winning even more Super Bowls.
8. NFL films. For decades no other sport had anything like it. Some still don't.
7. Rules changes in the late 1970s, to open up the offense: limiting contact between defensive backs and wide receivers, allowing defenders to only jam receivers in the first five yards of their route. Also allowing offensive linemen to use their hands to block instead of keeping their hands on their chests.
6. Astroturf greatly sped up the game, and made the TV experience more enjoyable. Later field turf helped cut down on injuries.
5. Instant replay allowed fans to better see what happened. Later replay helped minimize bad calls by officials.
4. Paul Brown was innovative, developing new plays, held the first classroom meetings, invented facemasks, and created two franchises: the Browns and Bengals.
3. Free agency. Like when Deion Sanders signed with the 49ers. Or when Deion signed with the Cowboys. Or the time Deion signed with the Redskins. Or later when Deion signed with the Ravens.
2. Television helped birth generations of new fans.
1. The NFL / AFL rivalry in the 1960's, eventually leading to the merger. Teams bid on players and created fan interest, like Charlie Gogolak and later Joe Namath.