Tapulous said its very popular Tap Tap Revenge has been downloaded more than 20 million times and played a total of more than 600 million times. The game is similar to “Guitar Hero” or “Rock Band,” where you tap the screen to the beat of the song. While the numbers can’t be independently verified, comScore said in April that Tap Tap Revenge was the most downloaded iPhone and and iPod Touch application at the time with 34 percent of all users downloading the free game. Tapulous’ figures are a bit outstanding given that Apple (NSDQ: AAPL) has sold more than 50 million iPhones and iPod touches, and the mobile applications business has been shaky at best. Although downloads are frequent, prices have been driven down by competition and consumers’ unwillingness to pay a premium.

Tapulous, which has only 20 employees, has raised only $2.8 million in venture capital from such investors as Salesforce.com CEO Marc Benioff and Khosla Ventures. In an interview with Reuters (NYSE: TRI), Tapulous’ CEO Bart Decrem was extremely bullish, saying that he expects to benefit from the rise of mobile app commerce, much like how Zynga, Playfish and Playdom have benefited from commerce in social games. Decrem: “It’s going to be big and all of a sudden people are going to say, ‘holy cow, where did those guys come from?’”

In addition to company’s flagship game, it has also had a number of high-profile deals. 20th Century Fox partnered with Tapulous to publicize the launch of “Jennifer’s Body,” a high school thriller, featuring Meagan Fox and Amanda Seyfried. Tapulous also signed a deal with Universal Music Group, to make games based on some of the label’s most famous artists. The first game was based on hit singer Lady GaGa and will include 14 songs for $4.99.