1. Everybody can play it. You don't need to be a genetical freak. If you're small or tall, it doesn't matter, as both have advantages and drawbacks. It's the the most inclusive sport possible.
2. It's a social game. Humans are social animals, and Football is the perfect team sport for them. The constant flow of the game, the subtle intricacies of simple but sophisticated rules, will make the most cohesive teams, where everybody is a friend, always perform better than problematic teams.
3. Amongst the animal reign, Human beings are puny, weak and slow. But they physically excel in one thing: endurance running. And Football perfectly embodies this very unique Human advantage and makes perfect use of it.
4. It's a thinking Human game. As said by the legend Johan Cruyff: "You play football with your head, and your legs are there to help you". And that's true, players must constantly use their mind, another gift from evolution, to resolve a match.