Firstly, in democractic government system, corruption is less likely to exist, because the officials are elected and if they are corrupted we can have them sack easily, something that can't be done in most dictatorship government structure. In Europe for example, corruption was the middle name of the rulers, until constitutional monarchy was been introduce. In Asia, despite according to the law, the Senate can vote an Emepror out of power if he failed to work in pubic interest, getting rid of a corrupt Emperor, still frequently require civil war.
Secondly, more compedent people in charge, although not all leaders elected in democractic govnerment, is necessary the best candidate, overall the rulers of democratic government are generally more compedent then dictatorship ruler, a King might be a wise and good king, but his son might not be as wise, as his father and the following son might once again not be as wise and might not even be compedent of the job.
Thirdy, the country is rightfully the property of the people, democractic goverment structure, reflect that the best, amount all government structures that exist.