Backflip Studios may have a stellar reputation for developing enjoyable free games, but even they have to be taken aback by the numbers their latest title has produced. In an article compiled by Mobile Entertainment, the studio has confirmed that Ninjump surpassed the 2 million download mark in its first week on the App Store.

“It’s been our strongest launch to date, far surpassing what we initially saw with Paper Toss,” Backflip CEO Julian Farrior tells Mobile Entertainment. Farrior also confirms that the game was played 10 million times in that first week, with the average play session lasting 5 minutes.

Reaching the two million mark in such a short period of time is a staggering accomplishment. Angry Birds, one of the most popular paid games on the App Store, has seen less than 7 million paid downloads since its launch last December. By contrast, Backflip’s most popular free game Paper Toss has already been downloaded more than 24 million times.

Numbers like this make a resounding case for game developers to give the free route some serious thought. In-app advertising might not be the most profitable strategy in some respects, but if you have an enjoyable enough product, Backflip has just proven how quickly a free game can spread.

[via Mobile Entertainment]