Each of the leaders wanted slightly different things.
Clemenceau was angry that Germany had done so much damage to France and wanted to punish Germany heavily to make them pay.
George wanted to weaken Germany for two reasons: he wanted to appear on the side of the British people who were now very anti-German and he wanted to stop them from being powerful enough to cause another war. However, he did not want to punish them as heavily as France did. This was because he knew that Germany was still an important country in Europe for trade and to stop the spread of communism. He did not want to cripple them so much that they had to find a radical alternative.
Woodrow Wilson was not very interested in the affairs of Europe and simply wanted a long lasting peace. He therefore did not want to anger Germany.