I suppose one way to distinguish WWI from previous global conflicts is it is the first war where independent states outside of Europe (I'm really counting all the Mediterranean as Europe so we can avoid random things like the Punic Wars) fought in the European theater as opposed to just their respective areas.
Of course, I'm not sure why that would be important. Most of the fighting, like the fighting in Africa and Asia, were colonial fights and not really all that different from the Seven Years War. And, in WWII, most powers were limited to their spheres. Really, the only thing different is that the United States, as an independent power, fought in Europe. I'm not sure if that really should matter.