Disclaimer: It is just my personal opinion about religion. 

Who is Jesus?

Some say that he is a man who lived 2015 years ago. He was a kind hearted person. He forgave his enemies and sacrificed his life for his fellow human beings. Read The Holy Bible for more info.

Who is Ram? 

He was the reincarnation of Lord Vishnu. He was a good man, who loved his family. Oh, he is the hero of another famous book, The Ramayana. 

Why do people pray to them? Why do people fight in the name of these heroes from novels?

Yes, there lived a good guy, Ram. There lived a badass guy named Ravana. There lived a fierce yet good guy named Narasima. People exaggerated their characteristics to make the novel interesting. We cannot make a deity out of every book we read!

Who is Harry Potter?

He is an awesome kid who learnt magic. He can fly on broomsticks, go invisible wearing a magical cloth. You can read more about him in the Harry Potter series of books. May be 2000 years later, people will make him Lord Harry Potter and celebrate his birthday!