The private market value for venture-backed Farmville and Mafia Wars developer Zynga has surpassed the public market value of Electronic Arts, signifying a continuing consumer shift from packaged video games to online social games, a new report said Tuesday.

Bloomberg BusinessWeek cited SharesPost, an exchange for shares of privately-held companies like Zynga, which states that the San Francisco-headquartered company has an estimated value of $5.51 billion, greater than Nasdaq-traded EA's $5.16 billion value.

This valuation is based on the SharesPost's indications on the price of shares in Zynga trading on the closed, private market, largely from Zynga employees, since the company is not yet public.

Zynga generates the majority of its revenue from the sale of virtual items in games like Farmville, Mafia Wars and FrontierVille, which players access through social networks like Facebook. An analysis at Business Insider in April this year estimated that Zynga's revenues would jump 70 percent year-on-year to $525 million in 2010.

There has been continuing speculation this year that Zynga is positioning itself for a public IPO. This latest value estimate at the company's private market cap is higher than other estimates that placed the company's value anywhere from between $1 billion and $5 billion.

While some may be skeptical of the supposed value of Zynga, ThinkEquity analyst Atul Bagga told BusinessWeek, "The valuation is not that crazy, given what’s going on in the market. ... It’s not that terribly expensive seeing the growth prospects." He projects that the virtual goods market will reach $3.6 billion in three years.

EA has realized the potential of the social game market, however, with the 2009 acquisition of social game maker Playfish for up to $400 million, including $100 million in performance-based earnouts.