The gauntlet was thrown at the end of 1977’s “Annie Hall” as Woody Allen and Diane Keaton held their terminal squabble in a health food restaurant on Sunset Boulevard.

“Why would you want to live out here?” Mr. Allen whined. “It’s like living in Munchkin Land.”

“What’s so great about New York?” Ms. Keaton shot back. “It’s a dying city.” Then she went in for the kill. “You’re incapable of enjoying life. You’re like New York.”

It’s something of an eternal showdown between New York and Los Angeles; like heaven and hell in the Middle Ages, they provide the poles for the American spiritual compass. As Mr. Allen might have asked, do you sell your soul and move to la-la land or stay in concrete jungle and maintain your integrity? Do you abandon all human dignity to live in the gritty city, or move to the promised land where it’s always 78 degrees and you bathe in fresh orange juice every morning?

To judge by the movies, this is no longer an epic battle, it’s professional wrestling: all show and no substance. The L.A./New York debate that galvanized “Annie Hall” is now just another Hollywood fiction.

Michael Mann buried the axe with 2004’s “Collateral,” in which Tom Cruise, playing a hit-man, tooled around nighttime L.A. in Jamie Foxx’s cab. Mr. Mann is known as one of the most authenticity-obsessed directors in the world; he actually had Mr. Cruise kill people to get into character. And yet he’d ignored a fundamental fact: No one takes a cab in L.A. No one. Cabs have belonged to New York ever since Martin Scorsese’s “Taxi Driver,” and the fact that Mr. Mann didn’t care anymore meant that no one cared.

Regional cinema was once a viable notion, with a variety of movies made for America’s different distribution circuits. Inner-city theaters received a steady diet of martial arts and blaxploitation flicks, Southern drive-ins got moonshine movies and gory horror films, college towns bloomed with hippie flicks like “El Topo” and “Pink Flamingos.” There were hometown directors who made hometown films: George Romero and his Pittsburgh zombies, John Waters and his gang of Baltimore freaks, Mr. Scorsese’s New York toughs. Even up into the 1990s there was Victor Nuñez and his Florida fables.

But in the past decade, America has blurred into one long strip mall. A movie like 2006’s “Something New” was set in L.A., but with its freeways, coffee-shop chains, cookie-cutter office buildings, and detached bungalows, it could have been shot anywhere.

Money, as always, is the source of the original sin: New York and L.A. are expensive cities, so most productions shoot elsewhere and try for a New York-ish or L.A.-esque look. If you saw the Olsen twins’ vehicle, “New York Minute” you might have noticed that New York looked not at all like New York and very much like Toronto, where it was shot. Digital manipulation allows filmmakers to set a movie like “Spider-Man” in New York but film it in Cleveland, New York, Hollywood, and Chicago, then digitally stir it all together to create Faux York. In Korea, they’re putting the finishing touches on a monster movie set in L.A. with almost every shot created digitally, so you can expect the results to resemble a bus tour of the city with anonymous interiors, mind-bending geographic anomalies, and the occasional shot of the Hollywood sign or the Capitol Records Tower to remind us where we are. To audiences, New York and L.A. look like everywhere else because more often than not, they are everywhere else.

But the biggest culprit in the blurring of the two cities is the lack of imagination on the part of the filmmakers. The best portraits of New York and L.A. have always come from directors with a surfeit of imagination, like the L.A. of the future in “Blade Runner” or the medieval Manhattan of “The Fisher King,” but usually you’re stuck with the geniuses behind Brittany Murphy’s “Uptown Girls” or Lindsay Lohan’s “Just My Luck,” and the insides of their heads are alarmingly empty. Their L.A. is a city where everyone has pools and lives in the hills, looking down on the city lights, and their New York resembles Norman Rockwell’s small town America, but stretched vertically. Only Spike Lee still seems to be interested in translating New York’s pushy street mobs, snarled traffic, crummy pizza joints, and delis into a cinematic portrait of the city. Only Quentin Tarantino seems capable of accurately depicting LA’s sprawling parking lots, sun-baked sidewalks, and endless diners and doughnut stores. Everyone else builds an imaginary city that’s as bland as the movies they’re making.

And their fantasy cities rarely include black people. One of the greatest benefits of city living is that you share subways and offices with people who don’t look like you, but most moviemakers imagine monochromatic cities. “Crash” was hailed as a bold new vision of L.A. because it actually took a different exit off the 101 and shot the city’s multicultural masses. And it took until 2004 for that most New York of directors, Mr. Allen, to give a black person more than a handful of lines in one of his movies.

To Hollywood, New York and L.A. are repositories of landmarks to be destroyed or fetishized when necessary. If you want to know what the two cities are really like, watch a reality show like “The Surreal Life” or check out a low-budget TV production like “Law and Order,” but stay away from the movies because they’ve got too much money. And too much money in the hands of people with no imagination doesn’t corrupt so much as it makes everything look exactly the same.