It was indeed a question that left Joshua wondering for ages.
This world had many gods, their titles countless but varying, which in turn gave them different aspects. Even without taking other gods into consideration, the contrasting aspects in titles was obvious even amongst the Seven Gods of men.
For one, followers of the God of Power and Justice could gain a series of divine spells that counter evil and Chaos while also attaining the ability to control. Another fine example would be the priests of the God of Love and Hate—they could charm beasts or even daemons, as well as interact with the dead or summon heroic spirits to protect themselves.
To list the others would be merely to be repetitive. In short, it is the different facets of the gods that earned them worship in different lands.