It’s been no secret that many of the Facebook platform’s stars have had a hard time reaching the same level of dominance on iOS where mobile-focused companies like Rovio, Pocket Gems and Storm8 have flourished.

But perhaps the 800-pound gorilla of the social gaming world, Zynga, is starting to get some things right.

For example, at the beginning of the year, the San Francisco-based company’s poker app hovered around the 50s on the top grossing list. It was being trounced by Texas Poker from Siberian developer (yes, Siberia) Kamagames Ltd. But now Zynga Poker has climbed to consistently rank in the top 5 over the past month and was even briefly #1 yesterday in the U.S.

With Zynga’s acquisition of Newtoy, the company bought Words With Friends, an app that is a reliable top 15 performer on the grossing list. The studio, which became part of Zynga With Friends, also just launched another hit last week called Hanging With Friends, which is now #4 (see right).

And today, the company’s introducing a mobile extension of its CityVille franchise called CityVille Hometown. (You can check out our coverage of the new title over on Inside Social Games.)

In a conversation yesterday related to the launch of CityVille, Zynga’s general manager of mobility Justin Cinicolo said that the rise on Apple’s top lists happened because the company has been better about taking customer feedback into consideration.

“On the web, it’s really easy to submit customer support tickets while it’s much more difficult on mobile,” he said. “The biggest factor has been listening to our users, figuring out what they want in the games, and addressing crash logs.”

He added, “It can be as simple as adding a confirmation button in the payment flow to make sure that people don’t accidentally purchase things. It’s primarily about usability.”

Cinicolo also said the company has been more focused on designing games with mobile devices specifically in mind. The CityVille Hometown app, for example, is a standalone app with a homier, smalltown feel that can be played without any connection to CityVille on Facebook. There are hooks, of course, between the two games that will allow for some cross-platform play. For example, Cinicolo said there would be cross-platform messaging and giftable items as well as specific help requests that only iOS players can fulfill.

But the app itself was designed by Zynga Mobile, a separate studio that coordinated with the Facebook CityVille team.

The CityVille brand, with more than 90 million monthly active users and 18 million daily active users on Facebook as recorded by our traffic tracking service, AppData, should theoretically have a large audience familiar with the title awaiting it on iOS. But success on one platform hasn’t always translated to success on another. The company’s staple FarmVille title for example, was eclipsed by other farming games like Playforge’s Zombie Farm on iOS.

This picture looks like it may be beginning to change, perhaps because mobile titles are starting to become more lucrative relative to social gaming titles. Another big social gaming company Playdom recently launched City of Wonder on iOS and it’s been able to maintain a Top 50 ranking on the grossing charts since its release three weeks ago.

A top-tier mobile game can earn $3 million more or month when considering in-app purchases, advertising revenue and offer walls, according to sources from the largest third-party service providers in ads and offers. Glu Mobile, a publicly traded mobile gaming company that can be seen as a bellwether for the industry, projects that it will earn between $8.25 and $8.75 million in smartphone revenue this quarter. On an annualized basis, that’s still small relative to what the largest companies will attract on the Facebook platform, yet growth opportunities and momentum are clearly behind mobile. Both growing adoption of smartphones and the way that Facebook has curbed virality over the past two years are making iOS and Android more attractive places to be.