Meanwhile, three-year-old Casual Collective, too, is taking aim at the more traditional gamer "instead of going after the same piece of the pie that others are after," says CEO Will Harbin. "I mean, there are so many FarmVille rip-offs -- or, at least, games with similar mechanics -- that we decided to take a more traditional approach to game development on Facebook. We're going after the user who CityVille really doesn't appeal to."

Harbin believes his core audience is the traditional hardcore gamer -- about 80 percent male and, of those, 60 to 70 percent in the 20 to 40-year-old age range. In order to cater to that demographic, his team has repositioned its most popular game, Backyard Monsters, in the past few months, "making the monsters more cool-looking and less fluffy and cute, adding a bit more violence, and so on," he says. "The result has been higher user numbers for the audience we're after." He says he'll keep that in mind as new games are released.

Casual Collective has two games on Facebook -- Desktop Defender and Backyard Monsters -- with its third, Battle Pirates, currently in alpha but poised to launch a public beta later this month.

"We're loading Battle Pirates up with cool-looking fleets of ships, missile launchers, rockets, guns, ripper cannons, things like that," he reveals.

While Harbin, too, chose not to reveal actual dollar figures, he says he is very pleased with how Backyard Monsters is doing. "It's probably making more [average revenue per user] than CityVille but less than Kingdoms of Camelot.

"What I can say is that it's been meeting all of our growth targets; we're close to about 900,000 daily active users. I expect that it will peak at around 2.5 million in another few months as long as everything continues to go as planned. In addition, we have close to a 30 percent ratio of DAU to MAU; I don't know of any game at that scale that has anywhere close to that engagement."

The bottom line, says Harbin, is that a developer doesn't have to be in the top five or even the top 10 to be a success on Facebook.

"Because Facebook is huge -- with at least 700 million registered users -- you can build a very successful company with just a few million monthly active users," he explains. "You don't have to be a Zynga, even though I'm sure everyone wants to be the one to knock them out of the pole position. There's a lot of open space for developers to capture the more traditional gamers -- users who are used to playing Xbox 360 or PS3 but now want to have a similar experience in a mobile, more accessible environment."

Backyard Monsters

Fuzbi's Edery shares very similar advice with developers anxious to succeed on Facebook but who are finding it's not as easy anymore to get the attention of users.

"Not only have Facebook's viral channels been crippled, but you are competing against big venture-funded companies, as well as publishers, that are spending millions upon millions on advertising to suck up the eyeballs," he says.

"What I recommend is focusing on an under-served niche," he explains. "If no one else, for example, has a great submarine game, that's what you need to make. Then go to all the submarine fan sites and announce that you've got a great new game and to come check it out. That's a much easier path than trying to build the next CityVille that will appeal to 100 million users.

"Hey, if you think you can create the next mega-hit, knock yourself out!" he says. "But just understand that you're competing with big companies with lots of money to spend. Just recognize that you're picking a big fight!"