I don't think there's a movie out there with as convincing a futuristic world as Blade Runner. There's ones that are shinier and ones with bigger CG budgets - or any CG budgets whatsoever - but I think, watching it today, it's pretty evident how well Blade Runner has held up. This gritty, congested, polluted futureworld - it lives and breaths; hustles and bustles; feels lived in. I've not seen anything like it since in live action, though Akira might be a good comparison in the animated realm. Even stuff like The Fifth Element has relied on its quirkiness - Flash Gordon style - to compensate for how the world just doesn't quite click.
Most sci-fi ages like mad. Watch any Paul Verhoeven film and its pretty evident when it was filmed, much as they have their distinct charm. I can't say the same for Blade Runner (nor Alien).
I think there's grounds to attack Blade Runner. I personally don't think so, but I could understand if someone wanted to describe it as pretentious or boring. Its looks? No, I don't see it. That's something which Scott still hasn't lost his knack for - even if he's directing shite like Prometheus.
I'd also like to use this opportunity to point out that both Alien and Blade Runner are available on blu-ray and look like they were filmed yesterday.