To Hitler and to fascists in general, the problem with democracy is that it gives power to people who do not deserve to have it.
Fascists do not believe in the idea that all people are created equal or in the genius of the masses. They do not believe, as democrats do, that the mass of people will generally come up with the right answers. Instead, they believe in the idea of the superior man. They believe that some people are born who are simply better than others. These people are the ones who are most fit to rule a country.
Democracy is bad because it allows the people who are not born with these talents to control and limit those who are born with what it takes to rule. Such people should not have to answer to the masses any more than parents should have to answer to their children or be controlled by their children's desires.
Therefore, fascists like Hitler think that fascist dictatorships are superior to democracy. A fascist dictatorship allows the superior person (of course, Hitler saw himself as this person) to rule over the inferior people in a way that democracy does not allow.