Waste of a list.
A ruler must be judged by several parameters-
Military achievements
Territory
Administrative feats
Public welfare and economic development
Legacy and success
Personal character
My personal list-
In no order as thats quite impossible
Cyrus the great
Caesar augustus
Asoka maurya
Suleiman the magnificent
Frederick the great
Caliph Umar
Justinian of byzantium
Peter the great
Emperor Wu of han
Akbar the great/shah abbas of persia.
Mentions-
Napoleon bonaparte[Misses out due to eventual failure,but terrific military and administrative feats and legacy]
Elizabeth I[Small territory,lack of military conquets]
Louis XIV[Died leaving france bankrupt,and didn't care for public welfare-peasants were oppresed.But increased political,cultural and military power of france enormously]
Genghis khan[Single handed nation builder,great military and territorial conquests,zero administrative or public welfare,utterly merciless to general humanity]
Victoria[The period of her greatness was mostly due to english nation,not qualities of monarch]
Charlemagne