I'm asking that because, with the exception of the defeats against Prussia and Mexico, he succeeded to raise France as a fully industrial nation, gave some rights to the workers (like the right of strike) and played a major role in the creation of both Italy and Romania. So why is he seen as incompetent ?
Napoleon III did a lot of things the "wrong way," even though he often got reasonably good results. He is remembered more for the first than the second.
For instance, he was elected as President in 1848, but became Emperor after a coup d'etat in 1851 because he wasn't allowed to run for other term. His first post coup years were repressive, although he later "eased up" on labor to allow strikes, foster industrialization, and rejuvenate Paris.
In foreign policy, he toppled the position of his own country, France, over a quarrel with Prussia over the Spanish succession, a topic that was basically "none of his business." This was arguably the worst diplomatic mistake of the 19th century, and more than offset his successes in the Crimean War and the Franco-Piedmontese war against Austria, which benefited other countries more than France.
To quote Marc Anthony out of context, "The evil that men do live after their deaths; the good is oft interred with their bones."
Napoleon III was President of France from 1848-1852 and Emperor from 1852 to 1870, a measly 22 years in total.
Napoleon I was consul of France from 1799-1804 and Emperor from 1804 to 1814, or fifteen long and glorious years, plus a hundred more days in 1815.
Napoleon III only managed to give France a mere 18 years of peace in his reign.
Napoleon I gave France a full year of peace in 1802-1803 during his reign.
So clearly Napoleon I was far superior.