Although they are all sun gods they still had many differences. With Apollo in Greek mythology he was seen as more of a metaphorical god, different from Helios their first sun god who they thought made up the sun. Unlike Tonatiuh who was viewed by the Aztecs as what supported their universe. Or Liza who made up the universe in West African mythology. In Egyptian mythology Re was their supreme god and was viewed by Egypitains as their manifestation.
Helios was the sun god who rode in a chariot. Until humans grew to understand science of the universe thats when,Apollo would become the metaphorical sun god.
Liza was the sun god according to the people of West Africa.It is believed that him and his sister Mawu created the universe. Re was the Egyptian sun god. In Egyptian mythology views on the sun as a manifestation, or their supreme god. Tonatiuh was the Aztec sun god he was the fifth sun, The Aztec's believe that he supported the universe.
Sun gods were very significant in early times because many of the cultures viewed the sun gods as who made up their universe. Without the sun gods who would they have thought made up their universes? So many cultures have different view points on sun gods because they all have different ideas on how their universe was created. And they all their own mythologies, for example the way greeks viewed their mythology was completely different from how the Aztec's viewed their mythology. If there wasn't different types of mythology the world would b completely the same.