Film sci-fi is often original, with stories that were made specifically for the screen, but there have also been many, many sci-fi adaptations. Many classic novels have been made into sci-fi movies, even previously thought unfilmable ones like Dune, but there are still many great sci-fi novels out there that have never made the leap to the silver screen. These books would make for excellent movies, or in some cases, series of movies.
They need to make books into shows and not movies, really suck when books you like get crunched into a 2 hour movie.