Blade Runner fits the definition of a
seminal science fiction film. It has inspired countless cinematic and TV imitators and defined a view of the
near-future so convincingly that a lot of people almost take it for granted that
it will be so*.
While BR's theatrical release "happy" ending was typical studio butchery (production was late and over budget and the completion guarantors (Bud Yorkin and Jerry Perenchio) pretty much had editorial control by that point), it did feature helicopter footage of majestic Alaskan scenery that went together quite stirringly with Vangelis' end-titles score. I've seen the movie several dozen more times and I prefer the Director's Cut, but the "happy" ending is cinematically effective if a non sequitur.
The aerial footage was actually shot by Stanley Kubrick for "The Shining". Being so late and over budget, Scott asked Kubrick if he could help, so Kubrick sent over something like 200 cans of film with only the proviso that nothing used in "The Shining" be reused in BR.
Continuity errors occur so easily that most filmmakers pay a rather large salary to someone who specializes in preventing them. Nevertheless, there's one in BR so big I can only assume they had no choice but leave it in: the different versions of the Voight-Kampff interview with Leon. The actual scene is one take, and all subsequent references to it are from another take. The first time, Leon says "Lemme tell you about my mother." Every time Deckard later replays the video Leon says, "I'll tell you about my mother." I think that's the only vocabulary change, but intonation and phrasing by both Leon and Holden are quite different. I think that either they had to later reloop the audio of Leon's VK test to use during scenes of Deckard's investigation; or, they shot the later background versions first, and then filmed such a great VK interview scene (and it does rock) that they used it despite the discontinuity. I'd be very interested to hear another explanation.
*ADDENDUM: 6 Feb 2001, this story on BBC website:
http://news.bbc.co.uk/hi/english/uk/newsid_1154000/1154662.stm