Italy joins the central powers in 1915. That's the latest I can think for the Germans to acheive a real and substantial "victory" in the traditional sense.
Austra-Hungary doesn't have to deal with Italy and can concentrate on Russia and Serbia, both of which get defeated quicker.
The Germans can concentrate, as a result, more forces on the western front, since A-H would be more able to fight the eastrn front competantly.
Germany and Italy launch a double offensive against France, with Germany winning a battle at Ypres and proceeding to attack Calais, and Italy attacks Nice/Savoy. If Nice/Savoy is a relatively easy catch, then Italy might go for Marseilles in the south or, if they are smart, Dijon in the North. If the Italians can take Dijon and meet with German forces in Alsace-Lorraine, then they can launch a third and final offensive. This would gut France and drive the British back to the coast (and maybe even out of the war).
If Russia wasn't already gone by this point, they could make easy work of them.
The war would end with Germany annexing Luxembourg and perhaps Belgium. If the Kaiser has big enough balls, he might decide to gobble up some northern French departments, and the rest of Alsace-Lorraine. There would be a network of puppet states in Russia, and maybe some Austrian territorial annexation there. I could imagine an Austrian puppet state in the Ukraine.
Japan might be made to return German Pacific islands.
Italy would certainly annex Nice/Savoy, and if they had enough balls, might even annex the entire area east of the Rhone.
I don't know if German would make many annexations in the east. Maybe Poland would be annexed as a semi-autonomous German state (similar to Bavaria).