There is little connection between download volumes and mobile game revenues

"Something fascinating has happened in the app industry over the past two years; download volume performance has decoupled from revenue performance almost entirely. A few years ago, the original Angry Birds spent 22 months in the Top 20 chart of biggest revenue generating apps in America. The latest Angry Birds game struggled to stay 2 months in the Top 20.
The app industry revenue generation is now utterly dominated by free downloads that lure consumers into paying for in-game features month after month. The top-grossing iPhone app in America, Clash of Clans, is merely #70 on the download chart. Ironically enough, this emblem of the new era of mobile gaming was created by Supercell, a Finnish company now located in the old Nokia headquarters. Just 50 feet from the Rovio HQ.
The extremes in the mobile app market are only growing more pronounced. Rage of Bahamut, an addictive card battle game, no longer makes it to the Top 1’000 of iPhone apps. Yet it remains the #14 app in America when it comes to revenue generation, far above the new #1 download app, Temple Run: Oz. Very, very few people download the Rage of Bahamut. But those that do end up enslaved by it. Industry rumors peg the daily average revenue per active user of this game to be as high as 80 to 90 cents. That is an amount of money that translates a free download to a massive cash cow even if it gets only 0.5% of the Angry Birds download base."
Source:  Forbes, 6th March 2013