By Maggie Shiels
Technology reporter, BBC News, GDC, San Francisco
Halo 3 sold over $170m worth of copies in the first 24 hours on sale
The world's largest social network has thrown down the gauntlet to game developers to design an iconic social game like Mario or Halo for Facebook.
Research suggests around three quarters of Facebook's 400m users play social games on the site.
The challenge came on the opening day of the Game Developers Conference.
"The next killer game is still out there and this game will come from you," Gareth Davis told a room of designers in San Francisco.
"When we look at every major game platform, we see that there is an iconic defining game on that platform whether it's Sonic or Mario or Halo.
"And while there are some great games on Facebook today, no one has yet produced the iconic game for [it]. The Facebook Mario is still out there," said Mr Davis.
But some developers questioned what exactly constitutes an iconic game.
"If I knew that, I wouldn't tell you the answer. I would go out and make it," said Pete Morrish of developer Waterfront Entertainment.
Dasha Kobzeva of Playrix Entertainment was a little more forthcoming.
Everyday 31m people play Farmville
"I think a good strategy game might be a winner but at the moment what we are seeing is a lot of games that are pretty similar to each other like farm games and aquarium games," she said.
"So far nothing really stands out."
But veteran games developer Brenda Brathwaite, creative director of the online social entertainment company Slide, disagrees.
"I think the killer game for me at the moment is Farmville. It is the biggest game that is out there and I would have to give respect to that."
Farmville, which is a virtual farming game, took five weeks to develop and attracts over 80m monthly users.
Mr Davis said while he cannot pinpoint exactly what the iconic game will look like, he knows it will have to have some key ingredients.
"We know it's going to be built on real identity and around real friends. It is a game that will appeal to everybody across the board and tap into social emotions and generate feelings you have never felt before.
"It will probably be personal to you because it will tap into all that information you have about you on Facebook."
Social games, where users play with friends and family, is a relatively new industry. Despite that, the sector has attracted hundreds of millions of users who do not consider themselves gamers and have eschewed the traditional off-the-shelf games.
Facebook lets users tap into their social graph
"It has grown to $1bn from nothing nearly three years ago. It is definitely a mass market phenomenon across the board and represents a change in the way people play games and interact with their friends," Justin Smith of research firm Inside Network told BBC News.
For many in the industry, Farmville has set something of a gold standard with its user base.
Mr Davis however predicted that in the very near future that number will be soon be dwarfed.
"We are going to see multiple games with more than 100m people playing each one. That is as many people as watched the recent superbowl, the most watched TV programme in American history.
"The growth we are seeing is amazing and in a short space of time we have developed a brand new mass market audience for gaming," Mr Davis told BBC News.