Why are Ramayana and Mahabharata so popular among Indians?
Ramayana revolves around Rama, the embodiment of righteousness, who faces challenges in behaving righteously because of his many roles and circumstances in life. Mahabharata says about itself "Whatever is here is everywhere; Whatever is not here is nowhere". If one reads and understands Mahabharata fully, then that is considered as one's complete enlightenment.
Ramayana and Mahabharata are the epics which teach Being Righteous will Save the Righteous. Rishis (Sanskrit word for Scholars) from Indian subcontinent perceived that any Evil in the society will lead to the killing of All their descendants in future. Inorder, to show the Righteous path to their descendants and help them live a peaceful life, our Rishis ensured that Ramayana and Mahabharata are popular among people from Indian sub-continent. I believe Ramayana and Mahabharata must be introduced as subjects in all schools across the world to inculcate righteousness in our future generations.
Now, let us come to the point: What is righteous?
Bible seems to have inspired from our Indian epics to come up with The 10 Commandments for the followers of Christianity. Whatever it is, GOD is The One who created All of us. So, we must All believe in Him and follow our religion to achieve Him, like the way several streams of rivers flow towards the ocean. The context behind the last statement is "GOD is an ocean and River is a religion".