The Elder Scrolls XVI: Sworn to Carry Your Burdens

[veti]

The best move here, from a cynical political powergrab standpoint, is to side with the Imperials, become a big famous soldier in the war, reunite Skyrim, then use your soldierly Imperial clout to marry Elisif and push your claim as Dragonborn, the one who retrieved the Jagged Crown, the Unifier of Skyrim, blah blah blah.

Although you could make the opposite move - side with the Stormcloaks and then marry Ulfric instead... That way you can have an independent kingdom.