Okay so taking the given suggestions lets assume for the moment that in the west the French and British co-ordinate better and win a decisive victory at the Marne, and in the east the Russians win a decisively at Tannenberg. The Germans are thrown into retreat and the Allies continue to advance. If the Allies are able to push on and beat Germany in a much faster and less bloody manner than in our timeline what are going to be the knock-on effects?
- Without the four years of blood and loss I don't think you'd get a highly vindictive Treaty of Versailles. A better guide would probably be the Treaty of Frankfurt that ended the Franco-Prussian war.
- What sort of territorial concessions would Germany have to make, losing Alsace-Lorraine is a given but would they try and push for more? I could see Russian demanding Posen to add to their Kingdom of Poland, perhaps Eastern and Western Prussia as well? Even Alsace-Lorraine and Posen is likely to cause bad feeling, add in territory on the left bank of the Rhine and Eastern Prussia and you've just created some nice little revanchist feeling to help set up the rematch at some point in the future.
- Russia buoyed by military victories and annexations is able to regain a small piece of stability, plus they don't have large groups of annoyed armed peasants standing about to rebel. Now the underlying problems with the country and its rulers are still there so it's simply more of a slight delay before some form of revolution kicks off.
- All of the countries involved aren't drive to near bankruptcy. Germany will be paying reparations so they're not so great but France and especially Great Britain will be much better off, IIRC it was the Great War that effectively sealed Britain's eventual economic decline.
- If it's over before the US becomes involved then no Woodrow Wilson or his bloody Fourteen Points. The US continues its isolationist course although its growing power gradually leads it to take more interest and active part in global affairs. What does this do for black culture? I have vague memories of black troops being effected by exposure to France during the war and Paris in the interwar years but don't really know.
- No Fourteen Points means interesting things for Austria-Hungary. If they're pushed into dissolving - and I can't really see a monarchy like Russia pushing for that, annexing territory sure but otherwise might set a bad example for the minorities - they can probably stumble on for a bit but they're separating fairly soon. Probably losing some territory to Russia, I've got no idea what they might want, and indemnity payments will unbalance things.
- For the British and French if it's over quickly and they don't have to call up large numbers of colonial troops what does this do to the decolonisation process? IIRC fighting and dying for their mother countries in Europe helped foster nationalism and a belief that they'd earned their independence. Even before the war in India you had the Indian Councils Act 1909 and later the Government of India Act 1919 so they were already very slowly moving towards independence. With the Indian National Congress continuing to campaign for better better representation and eventual Dominion status the colonies were on the way out, however with no war expect a much slower process which could be no bad thing.
- The German colonies will probably be divided up pretty much as in our timeline I would expect. Well that's most of what I can think of for the moment.

- Edit: One other factor I just thought of, with no years of slaughter the old order wont be so completely discredited to so many of their citizens. Socially that's going to have major impacts.
Hello,
the fastest way to crush germany is to avoid the early mistakes...
do not provoke the osmans - give em their battleships - offer even another pair in 1915... so they will not side with germany (big asb, because great britain and france want to destroy the osmans, also the russians hope for this... but this would help a lot, the osmans allied with entente means secure supply line to russia
also, make the french be not so idiotic with their plans and - also - make their generals far better... with this the border conflict is not the big pain in the a.. for them and they can beat the germans big at the marne.
combine this with mechanical breakdowns of the "dicke bertas"... so the antwerp-forts hold. with this, the german western army is really in deep trouble...
if this comes together with a better russian advance, esp. in the south, they can take out austria, without austria the germans are doomed in 1915...
but you make a mistake about entente-war goals.
they exist from day1 (even 10 years earlier)
the russians: they need sucsess to stabilize their nation... it is weak and without this, revolution is sure. So russia need to take land, from ah and germany... so no poland, just a fictional poland, part of russia
great britain need to destroy the (stronger) economical enemy... so they will take the german trading fleet, will force em to pay huge sums in gold and destroy important parts of the german economy... they need to do or germany will be economically to strong for them
france want "revenge"... destroying the big neighbour was the clear war goal from 1871. So no light peace...
versailles or worse, nothing else.
if the entente had been not tamed by the americans they had made "peace" even more cruel and brutal as they did. no "fair" peace is possible
but i bet, if they do some mad, like genozids and sterilisations of million people (ONLY chance to avoid german revenge, germany is just to strong economically), after that they will fight each other again.