It was not so much Napoleon himself as the events and forces he unleashed during his time in attempting to conquer Europe. Following the final defeat of Napoleon, the Congress of Vienna had attempted to restore as much of the Ancien Regime as possible. This could not be done, however, because of changes in political thought occasioned by Napoleon's invasions. Chief among these was the birth of nationalism. It was largely the result of the threat posed by Napoleon that led the people of Europe to see themselves as members of a particular culture which should be geographically defined. This birth of Nationalism resulted in the collapse of the old Austrian Empire, the brief appearance of the Austro-Hungarian Empire, and ultimately the series of alliances which led to World War I. It was also the appeal of nationalism which enabled Otto von Bismarck to unite Germany under Prussian leadership and also alienate France from Germany, a major implication for both World Wars.
The birth of Nationalism led to the birth of new nation states and ultimately a series of alliances intent on preserving the balance of power in Europe. This situation would not have occurred were it not for the havoc which Napoleon had wreaked on Europe.