If by "great" you mean influential, then definitely India's epics, the Ramayana and the Mahabharata would fit the bill IMO. Wikipedia has this to say about Mahabharata: > The Mahābhārata is the longest epic poem known and has been described as "the longest poem ever written".[7][8] Its longest version consists of over 100,000 śloka or over 200,000 individual verse lines (each shloka is a couplet), and long prose pass…
It seems that old writers had a different idea of storytelling. They were focused more on the theme & prosody[2] than the story. I think it set the bar very high since everyone know the base story. No wonder they had this complex structure and ideas for prosody[2]