Google+ is Google's most aggressive effort yet to crack the evolution of the Web from a place that connects people to information to a place that connects them to one another. It has amassed 20 million users in three weeks, according to research firm ComScore Inc. The addition of social games could liven up Google+, which has far fewer users than Facebook's more than 750 million and fewer bells and whistles. Google+ still requires an invitation.

The market for social games in the U.S., which reached $1 billion last year, is projected to reach $5 billion by 2015, said Pietro Macchiarella, a game analyst with market research firm Parks Associates. Much of the revenue comes from games played on Facebook.

Facebook requires makers of applications on its platform to pay 30% of revenue collected from selling virtual items on the network. One way Google could compete is by offering to take a smaller portion of game publishers' revenue. Google's success in recruiting publishers, however, will hinge on its ability to continue its momentum in adding users to Google+, Macchiarella said.