It's been three years since Supercell burst onto the top grossing charts with Clash of Clans.

The game which has been the top grossing game in the US, and probably globally too, ever since.

However, that reign looks like it's about to end, at least in the US.

Over the past couple of weeks, Machine Zone's more core strategy game Game of War has been stealing increasing amounts of time at #1 spot when it comes to the top grossing iPhone game in the US.

Of course, Supercell is fighting back. It's retaken the #1 spot on three occasions in September.

But it's not been able to sustain at the top spot in the way we've become used to.

Global reach

Of course, despite the call of games-as-a-service, a single game can't stay at the highly competitive top spot forever.

Similarly, in Japan, the longrunning #1 Puzzle & Dragons has been replaced by Monster Strike; but the demotion is only relative.

All these games continue to generate multiple millions of dollars per day.

Indeed, in the case of Clash of Clans versus Game of War, Supercell's game is still winning in terms of total revenue thanks to its much wider global appeal.

Taking a look at the German iPhone grossing chart, we can see it still nailed firmly into the #1 position while Game of War yoyos between #2 and #3 positions.

And in the three key Asia markets, Clash of Clans is well within the top 50 grossing chart, while Game of War doesn't chart in China and is now slipping out of the Korean top 50.

Nevertheless, if it does replace Clash of Clans as the top grossing iPhone game in the US, it would be a triumph for Machine Zone, which as well as working hard on retaining and increasingly monetising its audience, has been more aggressive in terms of its mass market advertising.

Still, recent research suggests both games are now in a mature phase that increasingly sees their revenues being generated from a falling number of active players, so maybe we should expect a more widespread shakeout at the top of charts as 2016 approaches.