Because of his power, authority, and cunning, Ra was the most powerful of the System Lords. Despite the animosity System Lords feel for each other, Ra was recognized as the Supreme System Lord, a title which made him nominal Emperor of the Goa'uld.
Spoiler warning: Plot or ending details follow.
After his death, the Goa'uld System Lords entered a power struggle that lasted for many of the early seasons of Stargate SG-1.
GateWorld's article on Ra in THE STARGATE OMNIPEDIA.