themanwithnoname on 23 September 2009
I think it's a combination of things. Positive word of mouth for sure, but for awhile and even to some extent currently it became one of "the games to get when you get on Xbox 360." There were no ifs, ands, or buts there, the Gears franchise continues to sell systems to this day, as it is talked about by many as the game that they'd get when/if they ever get a 360.
themanwithnoname's law: As an America's sales or NPD thread grows longer, the probabilty of the comment "America = World" [sarcasticly] being made approaches 1.
Essay Pro