Maybe you’ll always see whatever flicks you grew up on as being inherently better than the modern equivalents kids are enjoying now (even if they probably do look about the same, in the long view, to the unbiased viewer.) Nostalgia’s a real hard thing to rise above, so we’ll temper this discussion by saying that the wave of sci-fi movies profiled here isn’t necessarily better than those that have followed it; but its flavor is still markedly different.
By my reckoning, this golden or silver age of cinematic SF began with Alien, concluded with Alien3, and RoboCop 3 was the first flick to mark that it was over. This period’s comprised of movies like Aliens, Total Recall, Blade Runner, nearly all of John Carpenter’s movies and the first entries in the Terminator, Predator and RoboCop series. They all shared a sensibility tied up in the manlier action films of the time. They had a rugged toughness. They were hard-minded about their fantasy. They always had an element of horror. Their leads generally had a charming meanness. Their comic relief came with an acidic, satirical sneer, not a wink or a tongue in cheek.
Aesthetics defined these flicks considerably. They really picked up the “lived-in future” notion pioneered by Star Wars and ran so far along with it that, most of the time, you were liable to forget that the tech and the locations were designed by effects studios and not actual engineers with a whole host of real scientific considerations.
The Auto-9, the M41 Pulse Rifle, the Phase Plasma Rifle with a 40-watt range… they were all purposefully-designed, credible weapons that wouldn’t look out of place at a Heckler & Koch product showcase. When fans built their own Power Loader in their garages or illustrated cross-sections of ED-209 or worked out what design flaws Skynet likely had to overcome on the way from producing the T-600 to the T-1000, you figured they were simply picking up on all the thorough “imagineering” the movie crews had already done. Indeed, these flicks' attention to detail bordered on fetishistic.
Chalk a lot of this verisimilitude up to how a lot of these flicks shared the same personnel. Not only was it a time when a breed of concept designers and creature artists like Ron Cobb, Stan Winston and Rob Bottin truly reigned, it was also when directors like James Cameron, Paul Verhoeven and Ridley Scott were working out particular techno-fixations. Truly, this was the zeitgeist of the specific time, since that latter trio's later visits back to the genre like Hollow Man and Avatar haven't ever had quite this same attitude about their worlds (although perhaps Prometheus may be a return to form.)
One needn’t look at immediate spiritual successors like Independence Day, Waterworld or the Fifth Element and debate where the changes to the genre are - - thery're right there in all the sequels produced from RoboCop 3 onward. Alien Resurrection, Terminator 3, AVP, et al, all have markedly lighter tones and poke bemusedly at the world-building latticework their previous installments were so intense about setting up. Whether that's OK or not really depends on how seriously you took all this made-up stuff in the first place.
So why the change? It probably had a lot to do with external pressures. The senatorial hearings on the harmful effects of entertainment that started in the 80's by focusing on heavy metal and gangsta rap turned their attention to action flicks around this time. It got a little harder to reconcile RoboCop with his Saturday morning cartoon or the Xenomorphs with their action figure line. Hence, "hard R" sci-fi flicks slid down to "light R" and PG-13 sequels, and the leash likely curbed spirit just as much as behavior. In a lot of ways, the premise of RoboCop 2 (where Robo has to play nice according to 300 poltically-correct directives) came true for him and his pals.
Don't misunderstand - - there's been plenty of good sci-fi after this wave. They've been trippier, though; more fanciful. Their leads aren't an anxious command away from being outright killing machines; nor are they mothers who'll go to scary, psychotic lengths to protect their cubs. None outside of probably Pitch Black have embodied this particular quality of bleak, borderline-misanthropic danger in their characters and scenarios.
Was this a golden age of movie sci-fi? That's entirely up to your own taste regarding such speculative fiction. It was a distinct era, at the least, though- - one that stands in ever-greater contrast when put next to the flicks that followed it.