As a recent poll on ESPN reminded me, there really is no contest any more as to which is the most popular league in this country. It's the NFL in a walk. Now, while I might think that the end of the baseball season is more important, most people feel that any NFL game is really much more crucial. I would disagree with this, given that not even going undefeated in an NFL regular season guarantees you anything (apparently), but I'm in the minority. Here are my theories as to why the NFL reigns supreme.
Vegas: At some point in the past 15 years, Las Vegas stopped being the place where sketchy people left their money and people dressed like Elvis and started becoming Mantown USA. Everybody now knows at least one guy who had his bachelor party in Vegas. Apparently, there's nothing more testosterone laden than blowing half your life savings in a game of poker where you're WAY over your head. Football has always been popular with people who like gambling, and there's usually at least one show on the radio every Saturday that covers point spreads and gives a "lock of the week".
(of course, this is why ESPN was pathetically fixated on SpyGate last year. Oh no, can't upset the gamblers, right? They might break Stuart Scott's legs!)
Madden Football: Who doesn't love losing by 41 points to your friend who figured out how to throw a Hail Mary on every play? I can't tell you how many arguments and hurt feelings I've had over the years thanks to this game. But the vicarious thrill of making the Cardinals win a Super Bowl can not be beat. I just can't risk the heartache of getting killed in this game. Yet again.
Fantasy Football: Every guy (sorry ladies) it seems has a fantasy football team. And I'm willing to bet most of them are better than the train wreck I always end up with. It certainly adds interest to any Sunday when you see a guy on your fantasy team is doing well. Unless you're playing me, in which case, it probably doesn't matter. I believe I've gone six years without successfully making a trade.
College football: I'd be willing to put the combined national attendance for Division I (or whatever the hell they're calling it these days) football up against any sport in the world - yes, soccer included. Think about how many giant stadiums there are in college football. Clearly, this is a ready made audience for the NFL and adds some excitement to the utterly uninteresting NFL draft. Even someone like myself who did not go to a school with a football team will get excited every Saturday in the fall.
The other sports are hopelessly flawed: Baseball is extremely poorly run, has post season games that end slightly after midnight, and never figured out a way of dealing with steroids. Basketball is run in an even worse fashion, has playoff games that end even later and is mired in an officiating scandal that would - if the average American had any intelligence whatsoever - trump the MLB steroid scandal and Spy Gate. The NHL has relegated themselves to near irrelevance by a decade plus of suicidal decisions. NASCAR's popularity defies all logic but it still does not approach football. Golf is wedded to the spectacle of Tiger embarrassing everyone - without him, no one cares. Tennis is not popular and I have no idea why. The last remaining option is World Series of Poker tournaments from 4 years ago. Sorry, I'll pass.
Sunday: This might be the top reason why the NFL dominates in popularity. The games are on once a week, usually on a day that 95% of the population has off, and thus constitutes a "spectacle". It really doesn't matter if you lose even 60 baseball games. 1 football loss can be ruinous - just not as much so as in college.
Those are my ideas. Culled from various sources and of course, other people's arguments. Notice that I didn't put anything in about the game itself. While football can be fun to watch, it can also be a hopelessly irritating sludge of 1 yard runs, mindless penalties and endless commercials. No sport is perfect.