From an earlier answer of mine

No, Napoleon really was not "evil" in the way that Hitler or Stalin were. Napoleon's methods of imperial rule were far more ambiguous than that of Hitler's would-be imperium. Many Europeans under French rule sought to work with the Imperial system, whereas it was readily apparent as early as 1940 that German suzerainty meant a loss of national sovereignty, an economy predicated upon serving the needs of Germany first, and overall offered nothing to Europeans in return. One Napoleon-related joke that circulated in Vichy captured this zeitgeist quite well. When in a gesture of goodwill, Germany returned the body of Napoleon's son, Napoleon II, a number of Frenchmen wagged "the Germans have taken our coal, and all we have gotten back is the ashes." Napoleonic rule was harsh in many respects and seldom lived up to its Enlightenment ideals, but Europeans could, and did, accommodate to it with varying degrees of success. While French rule was generally unpopular, Nazi rule was decidedly loathed.

The great historian of Napoleon Pieter Geyl wrote his opus Napoleon: for and against during the German occupation and after his imprisonment in Buchenwald. Even though Geyl leaned towards against, he noted that there were elements of Napoleon's personality and charisma that still swayed him. This type of attraction really does not hold sway for Hitler beyond racist circles, and pro-Hitler sentiments are usually a type of placeholder for right-wing sentiments. It has become something of an axiom in Napoleonic studies that comparing Napoleon to either Hitler or Stalin almost always ends up benefiting the Emperor.

Rather than go into the vagaries of French imperial rule, for this question it is useful to examine the image of Napoleon in post-1815 literature in the arts. Napoleon's reputation underwent an odd trajectory in the nineteenth and twentieth centuries where he was first guardedly valorized and then denounced as a precursor to Hitler.

Napoleon's reputation in the nineteenth century tended to be that of a great man with great ambitions. Even in Germany, where memories of French occupation were part of the legitimizing process, recreations of Napoleon in fiction tended to have a Janus-faced character. While the conqueror was reviled in the works of Louise Muhlbach, one of the bestselling German novel writers of this period, she praised his almost bourgeois domestic life and devotion to his family. Although memories of the "Corsican Ogre" were still present in the Anglophone sphere, more sympathetic portrayals began to overshadow this negative picture of Napoleon. Both Carlyle and Walter Scott likened Napoleon to the great men of history whose own talents allowed them to remake the world in their own image. One of the woodcuts of Rebecca Sharp in Thackaray's Vanity Fair depicted her with Napoleon's iconic bicorne suggesting her ambitions to get her way in romantic conquests. This sort of attraction to Napoleon was not hard to understand for Victorian audiences; the picture they presented of Napoleon was one who appeared to master various social forces and movements and harnessed them to his own ends. Given the radical changes brought about by industrialization, the magnetism of such a figure was obvious. Napoleon had something a cult-like status among the emerging class of American industrialists. J. P. Morgan as a young man wrote his thesis upon Napoleon and the American nouveau riche became important collectors of Napoleonic memorabilia and art. The department store magnate Alexander Stuart, for example, shocked the art world in 1876 by buying Meissonier's Friedland, 1807 for a then unheard of price.

But this esteem and attraction for Napoleon did not mean that Europeans believed that the wrong side won in 1815. Rather, Napoleon's defeat and exile were the natural consequences of his hubris. Writers would often link Napoleon's obvious talents with his overarching ambition. When Napoleon appeared in Victorian juvenile fiction, it was often as a didactic warning against hubris. To be a "Napoleon" in Victorian society was to be a man who gave into the darker side of his own talents. A passage about Moriarty from Doyle's 1894 The Memoir of Sherlock Holmes illustrates this picture of Napoleon:

He is the Napoleon of crime, Watson. He is the organizer of half that is evil and of nearly all that is undetected in this great city, He is a genius, a philosopher, an abstract thinker. He has a brain of the first order. He sits motionless, like a spider in the center of its web, but that web has a thousand radiations, and he knows well every quiver of each of them. He does little himself. He only plans.

Even though Moriarty is an organizer of "evil", he is an ideal foil for Holmes. Beating a figure like Moriarty makes Holmes more heroic, which was a common narrative trope of British commemoration of their victories post-Waterloo.

The Entente alliance between Britain and France fostered a detente of sorts in Anglophone depictions of Napoleon. Boardman Robinson's cartoon Napoleon and Wellington: this time we come side by side evoked images of a spectral Napoleon and Wellington working side-by-side. The British press marked the centenary of Waterloo with praise for Napoleon and his legions and bemoaned the accident of fate that brought about conflict. But this highly complimentary vision of Napoleon was not to last into the interwar period. Not only had the arts and intellectual scene turned against "great man"-centric ideas (and this rejection had roots from well before the war- Nietzsche's writings on Napoleon stripped much of the mystique from him), but the wider zeitgeist had also turned against celebrating a man whose main accomplishments were military conquest.

The advent of Hitler meant that a negative depiction of Napoleon came to the fore in the interwar period. Wellington himself became the protagonist of the 1934 film The Iron Duke where he managed to save Europe from Napoleon despite the hindrance of unscrupulous politicians. The conquest of France heightened this depiction of Napoleon as a threat. The 1941 film That Hamilton Woman showed Nelson torn between his love of Emma and his duty, with duty winning out to the benefit of all of Europe. While the First World War denuded war of its glory for many, the Second World War cemented an image of Napoleon as a precursor of Hitler.

This less than complimentary portrait of Napoleon has proved quite lasting in postwar fiction. The postwar Napoleon is much a smaller figure and beset by various personal problems with the suggestion that he worked these out on the battlefield. Such pop-psychoanalyzing dovetailed with various theories on Hitler's behavior (i.e. "Hitler had only one ball", etc.). The 1954 film Désirée, featuring a very miscast Marlon Brando as Napoleon, shows him rejecting love in favor of ambition and the film's ending framed this as an incorrect choice. Napoleon's alleged short height became fodder for jokes, as exemplified by the 1956 cartoon Napoleon Bunny-Part in which Napoleon enters into Bugs Bunny's rogues gallery of short-tempered fools outfoxed by the wiseacre wabbit. In strong contrast to Doyle's picture of Napoleon, the author Ian Fleming saw Napoleon's shortness as key to his behavior. In the novel Goldfinger, Felming writes:

Bond had always mistrusted short men. They grew up from childhood with an inferiority complex. All their lives they would strive to be bigger than others who had teased them as a child. Napoleon had been short, and Hitler.It was short men that created all the trouble in the world.

While Doyle's superhero saw his mirror image in Moriarty's shade of Napoleon, Fleming's twentieth-century protagonist perceived little in common with Napoleon and his short ilk. In Bill and Ted's Excellent Adventure, Napoleon is short-tempered, cheats at bowling, and is fond of waterparks, which is quite as far from Carlyle's great man as one can get.

Even sympathetic depictions of Napoleon had to balance Napoleon as dictator. In the commercial flop Waterloo, Rod Steiger's Napoleon stomps around in his great coat and harangues his generals, again invoking Hitler, but the film gives him an inner voice that constantly expresses his doubts about his age and abilities. 2001's comedy The Emperor's New Clothes, Napoleon escapes from St. Helana and uses his firm military mind to restore the fortunes of a struggling green grocer he has fallen in love with, but the film ends spoiler with him rejecting gloire and embracing love and being content with being a grocer end spoiler.

The cultural weight of this interwar and postwar depictions of Napoleon greatly outweigh the impact of the more nuanced view of Napoleon that most historians put out. Napoleon as Hitler's prequel has some sway in pop history circles or conservative public intellectuals like Paul Johnson, but within the academy the general stance on Napoleon is best described as "constructively critical" in which is fairly negative, but acknowledges his accomplishments (David Chandler, taking an earlier saying about Cromwell, called Napoleon "that Great, Bad, Man"). But this portrait of Napoleon has much less prominence among the public than the tiny, temper tantrum-prone general or Hitler:The Prequel. This engenders a great deal of confusion when investigating the historical record of Napoleon and his rule, where he lives up to neither image.