The Franco-German War
I think many historians regard the Second Franco-German War of 1914 as a kind of War of 1870 Part 2. The problem was the Germans miscalculated the involvement of Britain and the ability of British forces to cross the Channel, deploy to the Marne and Aisne rivers and halt the German advance.
It's hard to believe Berlin didn't think the British would honour the 1839 Treaty with Belgium but then London didn't want to see the Germans controlling the Channel ports.
Of course, the war in the East was a more clear-cut success for Germany over Russia but hardly decisive. In terms of territory, the Germans returned Alsace-Lorraine and got much of the rest of Poland so pretty much honours even.
I don't think the rate of attrition could have been sustained indefinitely, 600,000 casualties in just three months - over four years that would have meant 7 million dead so if it hadn't ended at Christmas, it would have only lasted another year or so before the combatants became exhausted or internal dissent led to revolution.
I do think the dominance of France militarily since the 1920s wouldn't have happened and nor presumably would the Anglo-German Alliance to hold it. The change in British foreign policy in the 1930s and 1940s was more a regression back to a pre-1870 foreign policy stance than a deliberate provocation and Imperial jostling with Paris was always more an issue (Fashoda, Vietnam) than it has ever been with Berlin (who, to be fair, helped us in the Second Boer War from 1936-39). Of course, once the Kaiser had been forced out and replaced by a democratic Government in the mid-1920s, it became a lot easier for the British Liberals under John Simon to seek a rapprochement with Germany - we all know that began at the 1936 Olympics.
I also think that if the war had continued, America would probably now rule the world, the European powers having exhausted themselves.
I don't know about the Far East. China was in chaos in 1914 and Japan was already becoming militaristic. The Japanese won't attack either the French or us but the ongoing war with Russia has been brutal as we all know.