Suggestion for great gods in general: the current great gods are not the first and are simply the most powerful deities in existence. Previous great gods have either died or been reduced to lesser godhood for one reason or another.
Suggestion for two Great Gods
Sublimity-Through-Patience: Is the sun itself. An ancient deity, he retains a demeanour foreign to those of the current epoch, using a description in place of a proper name. STP is beyond a doubt, nearly unstoppable as a god as nearly all creatures have need of the sun and the life it brings. Despite this, STP maintains a hands-off approach to the world, having few lesser aspects in the world. The few he does maintain are inconspicuous and are usually difficult to identify as STP. Gods of justice, life, civilisation and order flock to his banner, though rarely does he aid them. When he does however, victory is almost always assured. If the Titan idea is pursued: STP is the Titan of Order who survived by editing his own soul. If chaos magic idea is pursued: several of those binding spirits are STP probing lifeforms on ihow to act 'godly'. His inactivity is partly due to his knowledge-probing and because he's also making sure none of the other Titans ever find out. The other half is that he genuinely likes his current role in the universe. If trickster god idea is pursued: STP answers all direct prayers with his godly incandescence. All petitioners have some learnt not to praise the sun. Instead, they praise his team of secretaries. Lesser gods and heroes are also regularly summoned by these secretaries to go on a quest with failure resulting in a redemption quest to fight the Titans.
Selene: an outcast amongs the great gods due to her youth, having ascended into greater godhood just before the last ice age and as such is still remembered as a mortal by her peers. Formerly being the ruler of a vast elven empire, her ascension resulted in the utter extinction of all pure elves, leaving only aberrants and other genetic oddities. In modern times, Selene takes the form of a giant spherical satellite that orbits the world, called the Moon. Before her ascendence, the world in fact did not have a moon. As a deity, she presides over the night, wisdom and knowledge. She is at significant odds with the other great gods due to her continued studies on the metaphysics of the world, especially godhood. This has resulted in a glut of weak-but-numerous gods under her command. If trickster god idea is pursued: Selene often raises random anythings to godhood for varying amounts of time. For purely scientific reasons, of course.