I saw it when it first came out nearly 30 years ago and at the time there'd been nothing like it. The grunge, the dark, the rain, the incidental technology. The look of lots of shoot-em-up games, not to mention films and comics owes a lot to Blade Runner.
As did I RPRT. Up until Bladerunner and Alien all sci-fi films were like 2001, pristine high technology, everything looks brand new and is lit brightly (with the possible exception of the Millenium Falcon in Star Wars). Bladerunner introduced the concept of high technology in decay. Ridley Scott said he got the idea from travelling the Atlantic in 747s for so long. He noticed that the planes started out nice shiny pieces of hi-tech kit but got progressively shabbier but still kept flying.
To me Bladerunner explores what it is to be human, e.g. how do you give an artificial life form the concept of empathy (which is what the Voight-Kampf test in the film is testing).
It also helps that, like a lot of Ridley Scott's films, its visually stunning. Take the scene where Priss is hiding amongst J F Sebastian's "friends" you could frame it and hang it on your wall. It figures that Scott started out as a set designer.
Bladerunner is also one of those films (like Apocalypse Now IMHO) which is better than the book on which its based.
Nice to know I've found something else with which to disagree with TJ