Battlefield 2 performed particularly well on Steam, as EA specifically devoted a lot of resources to make PC players happy, unlike other publishers who simply port a title from console to PC with little thought for extra tools or features.
Here is a game that eschews much of what defines the modern shooter genre, that promises an infinite number of customization options, that gives players the capacity to create not just elaborately defined action heroes, but entire worlds and games using the same tools that the developers themselves use in their Unreal Engine 4 action title.