There is a saying that a chain is only as good as its weakest link. A democracy is only ever as good as its weakest members. This can be a major disadvantage to democracy, a government that is based on the idea that the majority is always right. From an intellectual perspective, sometimes the majority is not right, it is simply the majority. Democratic decisions can be made for any number of reasons, not always the best. Other forms of governments such as socialism, benevolent dictatorships, and republics offer benefits that democracies do not. All forms of governments, however, have at least some drawbacks.
Yes, better forms of government exist besides democracy. A true democracy requires input from every member of society, which can become unwieldy quickly, particularly if there are a lot of potential laws to pass. A republic allows the election of leaders to make decisions for the rest of society, allowing for more efficient passage of laws.
Throughout history, leading political thinkers argued that potential forms of government exist that are better than democracies. These include a majority of the founding fathers of the United States, who established a democratic republic. Ancient philosophers like Aristotle argued that a government headed by a benevolent monarch represent the best form of government.
You can easily see why democracy is the best government that has so far been established by looking back at history. If all power is invested in a monarchy, the rulers become tyrants and form dictatorship. If left with an oligarchy or aristocracy, the few in charge tend to corrupt the system and put who they want in charge without regard to the people. In a democracy, however, the people choose their rulers, therefore the best choice for the nation is chosen.