Kinect Adventures. I'm serious. It sold 24 million. If you don't want to count a pack in. Then it's Halo 3. It sold over 14 million. Halo 4 did not come near that. Gears were never as big as people think they are. 3 sold 3 million. XBO was a dud of a console with flops. Remember when people were laughing at that brief window in time Splatoon was outselling Halo 5? On Wii fucking U?! XBO had a bunch of high profile canceled games. Once giants of series were now limp. Forza was the biggest thing they had but sill none of them sold as well as Halo 3. Best selling XBO game is GTAV at less than 11 million. No one is buying a Series X for anything. Even Sea of Thieves which is a success was also on PC soooo.
The real answer tho is Kinect Adventures and Halo 3. Halo 3 for sure moved hardware. Adventures is maybe the reverse but one way or another it is the best selling 360 game.
Bite my shiny metal cockpit!
