You put the Bhagavad Gita under fiction? That's rather offensive.
Though even in the standard Hindu conception, it isn't 100% factual reportage either. It is a conversation between Krishna Bhagavan and Arjuna on the battlefield of Kurukshetra as reported to the blind king Dhrtarashtra by his bard Sanjay as reported by the sage Vaishampayana to the sages of the Naimish forest as he heard from the sage Veda Vyasa the author of the Mahabharata (of which the Gita is a part.) And in the Gita itself, Krishna Bhagavan says it is the second time it is being told, the first being when he told it to the Sun who told Manu the first king, who told his son Ikshavaku.
Njal's Saga may have poetic embellishments but it is also mostly based on true events in Medieval Iceland.
If fiction is taken to be any writing which doesn't describe events exactly as they happened then we would also have to classify the New York Times as fiction (Not even counting the Jayson Blair stuff.) There needs to be a better word to describe the above works. Epic is more suitable IMO.