There is a vast difference between godly rulers and worldly rulers; much like between godly people and worldly people. Rulers are to look to the Lord Jesus Christ for the way in which they are to rule. The Second Psalm tells all rulers and kings that they are to submit to the Lord Jesus Christ lest they perish! Jesus is a just and merciful King!
What is the main differences between our King, and the rulers of this world? William Symington sums it up well in his magnum opus, Messiah the Prince:
Rectitude of intention characterizes all his (King Jesus') plans. Everything is designed for the good of his people and the glory of the Godhead. Other kings may have sinister ends to serve: even when doing what is right in itself, they may have an ultimate respect to their own personal aggrandizement, to the advancement of some favorite courtier; or, supposing they move solely by a regard to the good of their subjects, they may be seeking this at the expense of some neighboring state.