well, Ishgard was ruled by a Pope.

By the way, while checking for the proper definition of Sultan in wikipedia, they had the following ranking on the side:
Emperor = Caliph / Shahanshah / Padishah / Chakravarti / Chhatrapati / Samrat / Khagan
High King = Sultan / Maharaja
King = Emir / Shah / Raja / Khan
and more for lower ranks too.