Also half price deals on Castle Crashers, Battlefield 1943, Fruit Ninja Kinect, Geometry Wars and more.
The fastest game to reach the milestone on the download service.
Will 'definitely' look to Battlefield back catalogue 'first' for setting.
Castle Crashers, Trials HD, Hasbro Family Game Night and Shadow Complex also did well.
Microsoft says Worms 2 and Battlefield 1943 would have topped the retail charts on their release.