If we take a look at French writer Jules Verne's novel From The Earth To The Moon the story is not just full of imagination but has calculations which show how brilliant the writer is. A lot of the calculations which Jules Verne made came pretty close to what actually is - but he wrote about them more than a century before man ever set foot on the moon. Verne wrote about space, air and underwater travel before air travel and practical submarines were invented, and before practical means of space travel had been devised. Verne was not only a great writer but perhaps one of the greatest minds of his time.
Similarly, J. R. R. Tolkien whose work most of you are probably familiar with if you've read The Lord of the Rings series of books or watched the films by Peter Jackson. Tolkien not only wrote mythological adventure stories with great imagination but was also able to construct several languages unique to his stories.
Like Jules Verne, H.G. Wells also used scientific facts and figures in his writings, but what made his writings a little different than those of Verne were that he used psychology as well. He gets inside the head of his characters and helps the reader understand why the character is behaving the way he is and what's causing him to do the things he does - this can be easily understood if you've read his stories like The Invisible Man, The War of the Worlds, The Island of Doctor Moreau and The Time Machine.
Rudyard Kipling was born in Bombay, India to British parents, though he would live in many places throughout his life, he returned to India many times. Several of his stories and poems (The Jungle Book, Kim, Gunga Din, The Second Jungle Book, etc.) took place in India.
As fantastically imaginative as J.K. Rowling's Harry Potter stories are it's doubtful that she would've written a single word without doing the proper research on wizards and magic. Most writers are inspired by what is happening in their life at the time they're writing a particular work - in the case of Rowling, she used a lot of what she was going through at the time to write situations and characters for Harry Potter.
Sarat Chandra Chattopadhyay is one of the most popular Indian writers. His Devdas is easily one of the most recognized characters in Indian literature. Several of his stories have been turned into feature films in many Indian languages - Devdas, in particular, has been made 8 times in Hindi, Bengali and Telugu. Born into poverty in the late 1800s, Sarat Chandra wrote stories which took place in his present time and which were about the common man of that era - their struggles and triumphs - most of his stories were based on his experiences in Bhagalpur where he spent 20 years of his life. His lack of financial stability drastically effected his writings.
There have been very few novelists in India who can stir our imagination. Most Indian novelists today can't write sci-fi the way H.G. Wells or Jules Verne could. The few who are writing are not doing anything which one would consider creative. Once in a long while we get a great book or novel from an Indian writer, but how long must we wait before we have another classic at the same level as Devdas or The Guide? Today a novelist might be able to write a story that gets on the best sellers list, but unlike Devdas and The Guide, they're soon forgotten.
Although most novelists pick one genre and continue to write in that direction, a screenwriter must have the ability to write different genres if only to survive in a very competitive industry.
Perhaps the best example of a writer who could easily switch genres is William Shakespeare. It is widely accepted that Shakespeare has covered all the possible plots in his many years of writing. A playwright and a poet, Shakespeare has written 38 plays, 154 sonnets, 2 long narrative poems and several other poems. Shakespeare could write a tragedy, followed by a comedy followed by an adventure story better than anyone. It comes as no surprise then that most of his plays have been adapted into films. He understood his audience perfectly and in many ways was well ahead of his time.
The one thing to take away from this post is that it is extremely important to grow as a screenwriter. A screenwriter who is only able to write a single genre such as Romance, Drama or Mystery has not grown and soon will run out of ideas (there are only so many romantic scenes one screenwriter can write before he gets repetitive - this is why most Indian director have a hard time after their first two films - look at the struggling Sanjay Leela Bhansali, Karan Johar, Ashutosh Gowariker, etc.). Getting your mind away from a genre for a little while will also help you the next time you attempt it. If you've written a Drama, try your hand at Science Fiction next and then do a Comedy or Murder Mystery or combine a couple of genres (the results could surprise you). But always remember to research your subjects, your brain will thank you by taking your imagination to new heights...