I got this list from a great source - BrainPickings. You should check it for a treasure trove of info and writing and dreaming.
He also said that Huckleberry Finn is the best book ever written by an American author. So Twain does indeed get his props.
We all have to write. Whether you're an accountant or a filmmaker, in the digital age you'll be sending emails/texts/poems out to someone. How strong that skill is will in large part determine how far and wide you go. If you think you're a poor writer, nothing else will happen.
So practice. And start reading the greats.