Some games use the apocalypse as the Big Evil That Must Be Averted. Some games use the apocalypse as backstory to help establish a setting. Darksiders uses the apocalypse as its tutorial level.
Of course, seeing as how you're War, one of the Four Horsemen of the Apocalypse whose job it is to preserve the balance between Heaven, Hell, and Man before finally ushering in the End of Days, it does make sense that you'd feel right at home in the Final Days. Unfortunately for War, it turns out that he wasn't supposed to be ringing in the Endwar after all, and so he gets chained as a prisoner to face the wrath of his masters in the Council, and unleashed on the human-less Earth 100 years after the demons took over in order to right the Balance and get his revenge.