A few month's back during Xbox's Summer of Arcade, a little game called "Trials Evolution" came out. The game is a sequel to "Trials HD", which was also released as part of the Summer of Arcade back in 2009.
"Trials Evolution" did quite well for itself, instantly taking the "highest grossing day one sales in Xbox Live arcade history" for a few weeks until "Minecraft: Xbox 360 Edition" came out and took the title. Still, "Trials Evolution" was popular and like it's predecessor, only good sales numbers were expected from it.
Since the game's release, there's been a constantly influx of user created tracks and mini-games for players to download, and Redlynx themselves has released a DLC track pack for the game.
Thanks to always having something to do, "Trials Evolution" now has officially over on million in sales. The data appears thanks to the games global leaderboards, which show well over a million registered users for the game.
Ubisoft and Redlynx have yet to announce official numbers, but it's no surprise the game is doing so well. It's the sequel to a great game and has plenty of promotion behind it.