Spielberg's influence was boosted by his most recent film, "Lincoln," which earned 12 Oscar nominations last year including best picture and best direction, and managed box office collections of $275 million.
The magazine said the 67-year-old director's ability to attract foreigners to a U.S. drama about the back-room dealings and minutiae of 19th-century Washington politics spoke to his prowess. "Lincoln" grossed $93 million in foreign markets.
Forbes said that 47 percent of people surveyed rated Spielberg as influential.
"A celebrity's 'Influential' score represents how that person is perceived as influencing the public, their peers, or both," Gerry Philpott, president of E-Poll Market Research, which conducted the study for Forbes, told the magazine.
Winfrey, 59, who topped the list with 49 percent last year, slipped to 45 percent this year, which Forbes said could be due to her retreat from the spotlight while running her cable television network OWN.
Film director and "Star Wars" creator George Lucas placed third despite working little in the public eye in recent years. He sold his Lucasfilm company to Walt Disney Co for $4.05 billion in October 2012.
Directors Ron Howard and Martin Scorsese placed fourth and fifth on the list respectively.
Other high-ranking celebrities in the top 10 of the list included television physician Mehmet Oz, ABC TV journalist Barbara Walters and U2 singer and activist Bono.
E-Poll Market Research ranked more than 6,600 celebrities on 46 personality attributes.
Forbes did not say how many people participated in the survey.