Bladerunner is a classic because it is one of the pioneers in special effects n scifi, many films have emulated it and didn't even know that this was one of the sources of some elements....the pre-web idea that the people in the film spoke japanese and spanish to imply that the future is more of a world culture, ...fifth element did something similar....all of these artists like moebius and ron cobb introduced designs which are steeped in realistic cultures that brought a reality like nothing ever seen....giger's biomechanical style n designs were also completely "alien", to the viewing public in 79... Every other artist out there has been influenced by y these films generations later sand do not even realize... ,it was new and groundbreaking...it is slow by todays standards, but at the time was unlike anything we'd ever seen...
Same with star wars.... We are spoiled by internet, speed culture, instant gratification, quickly cut, visual effects today, but we forget that these special optical effects, and motion control technologies were novel ands difficult to accomplish, as those methods are still difficult by todays standards
But really makes these films special were the ideas that they presented, the moral questions that arose in light of these new situations and in the face of unique technologies and given god-like controls...these slow-moving films paved the way for many films that are considered modern classics and inspired many of our new writers, directors, n other artists in the industry today...n before the alien n bladerunner, star wars generation, there was the ray harryhausen / godzilla / flash gordon generation ...these are the directors n creators like g.lucas, spielberg, depalma, zemekis, coppola, cameron, r.scott...they've even influenced each other as well as the current gen of filmmakers, writers, engineers, inventors,etc
Bottom line, you'll appreciate the big chap more after watching alien....but do it when youre wide awake, bc it is slow by todays standards...films have to run under 2 hours now to maximize profits in theatres....they didn't care as much back in the day