How is European social democracy unlike Communism?

In what has become known as Communism there is one political party that has absolute sway over all decisions made. there is no accountability to the the public. In the system that is used by European country's there is an understanding that the people of a country won it and should be able to benefit from its success after all they are expected to look after it's security in times of war and peace. Keeping this in mind the wealth that is generated within one of these country's has to contribute to the well being of the people of the country not just the power and wealth of those that have managed to organise this wealth using the country's infrastructure. this is overseen by a democratic system where the leadership and laws of the country can swing this way or that as the people see fit not just as the political masers see fit. The average health and life span of the people in these country's is better then in country's that do not use this system so there must be something to it.