I think Ridley's right. As for the Western, it was never history, it was our fantasy of history, history as we wanted it to be, not as it really was. Sort of like "Prince Valiant" and "Robin Hood" weren't what the middle ages were about at all.

This is why "The Good, the Bad, and the Ugly" was the best western ever made. It was the compleat fantasy told in loving detail, using all the cliches and conventions of the art form. It took an Italian director who loved westerns to see what we Americans were too steeped in to properly understand.

Science fiction is not the history of the future, or even what we wish were the history of the future. Its a speculation of what the future will be like if certain trends today are allowed to develop without change or interruption. Using this definition, "Alien" wasn't SF, it was a very competent horror movie. "Aliens" wasn't SF either, but it was a terrific action flick. Their only concession to SF wasn't about the effects of technology on humanity. Underneath their suspense and action elements was a recognition of the chittering horrors that await us among the stars. The alien wasn't about tech. It was Life, and like all Life, it was hungry.

"Blade Runner" was real science fiction, a look at where we might actually be going, just like "2001" was a look at where we really needed to go, and "Star Wars" where we wanted to go.

SF is not dead, just as the Western need not be dead either. There's still much in those lodes to be profitably mined. My favorite western? "The Assassination of Jesse James by the Coward Robert Ford" (2007). I don't know how historically accurate it is, but it tells you everything you need to know about the Anglo-American psyche, before it was overwhelmed and diluted by the great Eastern and Southern European immigration of the late 19th century.