It appears if you make popular games for the iPhone and iPod Touch that you may luck out and bring in around $1 million a month.

Tapulous, the company behind the Tap Tap Revenge series of app games for the Apple devices, says that its games have been installed 20 million times now, and over 600 million games have been logged.

According to Reuters, the company has taken a round of funding at some point for $2.8 million.  Tapulous currently employees 20 people, but it sees nothing but growth for the entire industry, just as social gaming is currently growing with success stories like Zynga.

It is estimated that a full third of every iPhone sold has downloaded some form of Tap Tap Revenge from the company.  Their revenue comes from a mixture of sold apps, advertising in others and the sale of songs to their various games.

There is certainly something to be said for the "freemium" business model when it comes to the App Store, but of course the trick is getting noticed as the marketplace gets more and more crowded.  It’s doubtful many companies starting today could see this type of success, but those that have been around for a while may be able to ride the wave along with those who are already on their way.