Back in Daggerfall we had a choice of several endings, depending on our choices during the course of the game. All of the endings had been pretty different with
Spoiler Darth Vader is Luke's father
the the cannon ending being a mixture of all 6(?) endings. Since then, we have followed pretty liner quests with everyone getting the same outcome. However with the civil war we are given two very different outcomes, one Imperial victory and one Stormcloak victory.
I think the cannon history will be an Imperial victory with both Tallus and Ulfric dying in the war, but to calm agitation in Skyrim it is granted a special semi autonomous status in the Empire.