Did, say, the people of Spain view him as a great liberator, freeing them of the shackles of their ruling party? Or did they view him as just another war-warmongering, power mad dictator?
What a question! First, some scoping. At its height, the Napoleonic Empire consisted of half of Western Europe, including peoples rural and urban, speaking at least six languages and practicing an equal number of faiths. It would be hard to generalize. Instead, I will answer for the Jews. And in this era, when I say Jews, I really mean Jews living in middle Europe from Alsace-Lauren to Russia, where the vast majority of European Jews lived.
Regardless of geography, it is difficult to overstate Napoleon's impact on the history of European Jewry. An apt comparison is the role Lincoln plays for African Americans: a liberator by force. The enormous tidal wave of change Napoleon triggered also opened questions that minorities struggle with hundreds of years later: can I be a Jew/Muslim/____ and be a citizen? What do I value more - tradition, integration, or assimilation? How do I balance faith and public life?
But before all that: How and Why. How Napoleon emancipated the Jews is clear: through successive pieces of legislation in 1802, 1805, and 1806, and against tremendous domestic resistance, Napoleon unequivocally advocated that Jews be granted equality to other members of the French Empire. He restored a degree of self-governance under the guise of the Sanhedrin, essentially a community of Jewish elders, and encouraged Jews to engage with civil society by actively promoting them to important positions in military and domestic life. By 1807, Judaism was an official religion of France, along with Catholicism and Protestantism. In some cases, French soldiers literally broke the chains of German ghetto gates and declared the Jews could live anywhere they pleased. Why he did so is more controversial. Some scholars feel Napoleon was self-consciously projecting an image of humanitarianism and largesse. However, in private writings, Napoleon displays deep ambiguity and shades of anti-Semitism common to the era. Yet his actions are incontestable: Napoleon showed deft command of Jewish history, a sensitivity to the messianic spirit of the era, and a willingness to employ full citizenship over the medieval European model of anti-Semitic subjugation. And while his policies would vacillate between 1808 and 1810, by 1811, Napoleon's legal emancipation of the Jews was official policy.
In turn, Napoleon was beloved by the majority of Jews as a hero and liberator. Numerous Jews fought for Napoleon, some reaching the rank of General, including Marc-Jean-Jerome Wolffe and Captain Alexandre Marcquefoy who, according to one source, was awarded the Legion of Honor by Napoleon himself. Much of this enthusiasm is captured in (possibly apocryphal) oral histories which cast Napoleon as the New Moses. In one, Napoleon first encounters Jews while campaigning in Northern Italy in 1797-98. Napoleon sees men in Ancona wearing yellow hats and stars. When he asks a lieutenant who these men are, he learns they are Jews and wear the color and shape to identify themselves as such. He further learns they are forced by law to return to the ghetto by evening. Incensed, Napoleon orders a squadron of French-Jewish soldiers to break open the gates of the ghetto and declare all Jews to be free citizens. In another story, Napoleon encounters a synagogue of weeping Jews and is amazed to learn from a French-Jewish soldier that they weep for the destruction of their ancient temple. Napoleon vows that the Temple shall be rebuilt for such a pious people.
Jewish enthusiasm for Napoleon is further attested to in Gentile literature: Czar Alexander I tasked his officers with ensuring 'Jewish spies' would not feed information to Napoleon; Metternich feared Napoleon would be greeted as a 'Messiah' by Austrian Jews. Many of these claims were baseless (Russian Jews were famously loyal during the harsh war), but they imply an acknowledged historical oppression of a nation's Jews, and how different Napoleon's policies were.
The smaller contingent, but arguably better represented in Orthodox liturgics and religious scripts, react to Napoleon with apprehension. Rabbinical leadership in eastern Europe - Russia and Poland especially - were concerned that Napoleon's emphasis on cultural assimilation threatened Jewish identity. Certainly some Rabbinic authorities must have felt threatened that full citizenship for Jews would weaken their power, but there is evidence that many pious Jews considered Napoleon's 'freedoms' to be a truly existential threat. Rabbi Shneur Zalman, the founder of Chabad Chassidim, deeply opposed Napoleon on philosophical ground. Yet many other respected Rabbinical scholars such as Menahem Mendel of Rymanow were famous for praying daily for Napoleon’s success, if only because they thought he would bring the Messiah.
Sources:
The Golden Tradition: Jewish Life and Thought in Eastern Europe
Obstinate Hebrews: Representations of Jews in France, 1715-1815