Years ago, when I was first posted from Moscow to Washington, one thing preyed on my mind about the new assignment. How on earth would I ever understand that strange variant of football called gridiron? Not to worry, a colleague from an eminent US newspaper assured me. The game, he said, was the perfect metaphor for American life: long periods of committee meetings, punctuated by brief moments of extreme violence - and the whole package wrapped in gaudy tinsel. I too, he said, would soon be enthralled.

Alas, the finer points of the game still escape me, even though I've lived here for 11 years now. But the metaphor holds good, as will be obvious to anyone who watches the time-out team huddles, the bone-crunching blocks and all the other goings-on in Dolphin Stadium, Miami, due to start at 11pm UK time tonight. Yes, its Super Bowl time again: to be precise Super Bowl XLI. (The National Football League switched to Roman numerals in 1970, just in case anyone failed to grasp the gladiatorial, bread-and-circuses flavour of the occasion.) And this 41st Super Bowl, like every one in the past, will be the biggest one-off event in the American sporting calendar.

You can't approach the game without a suitcase of superlatives. The National Football League is the richest sports league on earth. Baseball has the history; basketball has the street cred. But football, beyond argument, is America's favourite spectator sport.

The festivities that precede the big game, lasting a full week, are surely unmatched in any sport anywhere. As for Super Bowl Sunday, it is a midwinter pagan festival to match anything the ancients ever dreamt up. A million bars, restaurants and homes hold Super Bowl parties. These have become a national institution in their own right, fuelled by beer and pizza, chilli and margaritas, and whatever else food writers concoct for their inevitable Super Bowl features.

The game commands America's biggest one-off TV audience of the year. Some 100 million people may watch today's game. The legal betting turnover in Las Vegas will top $100m (£50m); estimates are that across the country, in technically illegal office betting pools and the like, a prodigious $8bn may be wagered. If the on-field action is a bit dull (Super Bowls, like our own FA Cup Finals, have a habit of not living up to the hype), then there's always the half-hour-long half-time show, featuring anything from the Rolling Stones to Janet Jackson's nipple. This year, Prince is the prime attraction. And if nothing can take your mind off climate change, then you can always inspect the 3,000 mangroves planted by the NFL in the vicinity of the stadium - supposedly to make Super Bowl XLI fashionably carbon-neutral.

Then you've got the cheerleaders strutting their stuff on the touchlines, an American art form in its own right. And of course there are the ads during the half-time show, the most ballyhooed commercials on earth. Often they're more entertaining than the game; so they should be, given that a 30-second spot this year will cost $2.7m. The going rate for Super Bowl XL in 2006 was a mere $2.4m, note the specialists who monitor such trends.

But soaring ad rates are not merely proof of a flourishing economy. They also testify to the fact that this is an uncommonly interesting Super Bowl. For one thing, the Chicago Bears and the Indianapolis Colts, the teams doing battle this evening, both have wonderful story lines. "Da Bears", the most cherished sports franchise in the Second City, are making their first appearance since 1985, when they featured cult hero William "The Fridge" Perry, weighing in at 23 stone and with a smile as broad as his belly.

Those Bears were coached by the no less legendary Mike Ditka, who was wont to burst into the press room and ask the scribes whether they fancied a glass of champagne. When the reporters replied they were on deadline, Ditka testily commented: "You guys don't know how to live."

As for the Colts, all eyes will be on Peyton Manning, the quarterback who is said to choke on the big occasion, but marched his team to an epic 38-34 victory over the New England Patriots in the AFC championship game - semi-final for the Super Bowl - after they trailed 21-3. Now an entire nation (barring the portion of it resident in Chicago) waits to learn whether Manning can deliver again.

And then, in an astounding first, both today's teams have black coaches. Tony Dungy of the Colts and Lovie Smith of the Bears are close friends, and by common consent very nice guys. Far more importantly, their appearance is proof that not only on the field, but also in the most crucial jobs off it, the NFL is colour-blind.

For what it's worth, bookies make the Colts narrow favourites. But forget the result, and focus on the metaphor: the razzmatazz, the long sessions plotting strategy - which Condoleezza Rice has likened to generals mapping wars - and, of course, the violence. "I like to believe that my best hits border on felonious assault," Jack Tatum, a defensive back known as "The Assassin", once said. But in American football, and American life, quasi-felonious assault is just part of the package.