Facebook’s once-anonymous founders have moved from Silicon Valley start-up to the silver screen, in “The Social Network,” to the list of the wealthiest 1,210 people in the world.

The so-called Facebook Six, led by 26-year-old founder Mark Zuckerberg, have ridden the wildly popular social-networking site to amass a collective fortune of more than $20 billion. Zuckerberg, the youngest on the list, and his $13.5 billion, leads the six.

The young tech geeks are featured in the latest edition of Forbes magazine, which reports that while newbies like the tech wunderkids joined the elite crowd, the three wealthiest people in the world remain the same: Carlos Slim of Mexico, on top with assets of $74 billion, up a stunning $20.5 billion from last year; Bill Gates, now at $56 billion compared to $53 billion a year ago; and the Oracle of Omaha, investor Warren Buffett, at $50 billion, up $3 billion from last year.

Getting on the list, however, seems easier this year.

The Facebook Six’s fortune is based on the private share values of Facebook’s unregistered shares, which have skyrocketed from around $5 billion a year ago to as much as $50 billion in recent weeks. Critics claim the high values are distorted because only narrow blocks of private sales have been publicized in the past year.

The founder of Zynga, the social-network game developer, Marc Pincus, also hopped on the bandwagon this year with paper wealth of $1 billion based on his private, non-registered shares of Zynga.

Meanwhile, New York City lost its crown as home to the most billionaires. Its 58 uber-wealthy were passed by the 79 who call Moscow home. Los Angeles has 18 and San Francisco’s got 17.

Among the Big Apple’s big-buck folks, Mayor Bloomberg is no longer the city’s richest person, based on Forbes’ calculations. That award goes to the oil tycoon brothers Charles and David Koch, who are ranked collectively as tops in the city with $22 billion in wealth each — compared to $18.1 billion for Bloomberg, good enough for 30th place.

Overall, the world has produced a record number of billionaires. The 1,210 global billionaires hold a record $4.5 trillion in wealth, up sharply from $3.6 trillion a year ago.