What makes American football enticing to Americans is because it is so different from all the other sports games. Baseball and Cricket are similar games (not the same, but similar). Hockey, Polo, Football/Soccer, Rugby, Basketball...they're all very similar when it comes to gameplay - they're fluid. The difference between those sports is whether or not you use your hands, feet, or stick (and obviously rules) and the field of player (grass, dirt, ice, water, etc.). However, American football is nothing like Rugby and Rugby is nothing like American football.
American football is a game of strategy. Think of it as a war game. You have two armies, one offense, the other defense. Each one has a formation, has a plan. If you look at the formation of an offense team on the field, you generally have a strong center and your flanks are the ones attempting an envelopment. The defense has a strong center as well, but because they don't want to be flanked, they have guys spread out to catch those breakthroughs. The enticing part is that although you see the formations, they aren't always what they appear to be or they never go according to plan ("no plan ever survives the first shot").
Think of American football as a wargame and you suddenly realize why there are dozens of players per franchise and they are specialized into certain teams - offense, defense, and special. I am not saying that Rugby or Soccer or Basketball has no level of strategy. On the contrary, they do, but it isn't as planned/thoughtful as it is more fluid and reactive. Strategy in fluid sports depends on your one position throughout the game and the prowess of the individual player. Strategy in American football depends on the overall ability of the team with a powerful center, nimble flankers, and a strong and accurate commander.
I guess my point is, respect the sport for what they are, the concepts they hold, and the actual depth of play involved. Yes, to those who have never experienced the sport, or went to see the sport with a fixated mindset beforehand, it doesn't appear to be very fun or very interesting. When you look at a sport, look at the rules, watch the game, but above all, understand why those players play the game in the first place.