Before you say anything, this isn't a sales discussion. I know Halo 4 has sold 8m copies. From a sales perspective it is not a flop. But take a look at the latest Xbox Live activity chart. http://majornelson.com/2013/04/06/live-activity-for-week-of-april-1st/
Halo 4 has fallen behind Modern Warfare 3, which is a year older. So what happened? Is the online portion of the game just not that good? Too much of a Call of Duty influence? How would you rate Halo 4's online multiplayer?