There is a long period of debate which government system would be bestfor states. in this paper two main democratic government systems that exist in the wor!d will be addressed, they are the parliamentary system and presidential system. The place where the parliamentary system emerged and the best place to apply it is England. İn a similar way, the place where the presidential system has emerged and is best practiced is the United States. Therefore, First, the defining criteria of these two government systems and the historical development of parliamentary and presidential systems will be dealt with. The legislative and executive bodies of the United Kingdom and the United States will be identified and their working systems will be demonstrated to discuss which system is better. Each system should be assessed with the social, economic, political and historical values of each country besides the government system, which alone is not enough to make democratic, legal and powerful an individıtal country. This paper proposes that to discuss definition, historical development and comparison of two democratic systems and which democratic system is better for countries.