

The fantasy/SF line is pretty blurry. You can have dragons and robots at the same time. Others have mentioned Tad Williams and Zelazny already. I’ll add Melanie Rawn for dragons and magic, Charles de Lint for Faries in the modern world, and Christopher Stasheef for witches and terrible puns. And Tim Powers for a bit of everything!
I count those as SF. Romance heavy SF but still.