It is only the second time since 1995 that Gates has lost the crown, the magazine said, estimating Slim’s net worth at $53.5bn (£35.8bn), compared to Gates’s $53bn fortune, while investor Warren Buffett came in at number three with $47bn.
The trio regained $41.5bn of the $68bn they had lost the previous year, Forbes said.
The number of billionaires around the world has nearly recovered in 2010 after dropping by a third last year during the global financial crisis. There are now 1,011 billionaires, compared with 793 last year and 1,125 in 2008.
The net wealth of those billionaires grew to $3.6 trillion from $2.4 trillion last year, but is still down from 2008’s $4.4 trillion, according to the 24th annual Forbes list, which took a snapshot of wealth on 12 February to compile its ranking.
The average billionaire is now worth $3.5bn, up $500m from last year. And the number of women on the list rose to 89 from 72 last year.
The number of billionaires in the Asia-Pacific region grew by 80 per cent to 234 and their net worth almost doubled to $729bn, which the Forbes ranking attributed to the area’s “swelling stock markets and several large public offerings during the past year.”
“The global economy is recovering and it’s reflected in what you see in the list this year. Asia is leading the comeback,” Steve Forbes, chief executive of Forbes, said.