Of all the iconic moments in Jurassic Park, Steven Spielberg’s 1993 science-run-amok blockbuster, there’s one that functions as a perfect microcosm for the film’s legacy and appeal. It’s the early scene in which the characters—and, by extension, the viewers themselves—first catch sight of one of the park’s prehistoric attractions, a towering brachiosaurus. Logistically, it doesn’t make much sense: Dr. Grant (Sam Neill) and the rest of the visitors would surely have seen the mighty beast long before they pulled up right beside it. As movie magic, however, the sequence is beautifully staged, beginning as it does with Grant and Dr. Sattler (Laura Dern) lurching out of their seats, shedding hats and sunglasses along the way, to gawk at the impossible. They can’t believe their eyes—and neither could moviegoers, who had never seen special effects this… special before. “You crazy son of a bitch, you did it,” stammers Dr. Malcolm (Jeff Goldblum), neatly articulating the awe and disbelief of just about everyone in the audience. Spielberg had done it. He had brought back the dinosaurs.

For those of a certain age, seeing Jurassic Park on the big screen was a seminal experience, maybe as momentous as catching Star Wars in its initial run was for an older generation. (I was 9 years old when the film opened, in June of 1993, and will never forget the giddy terror I felt watching the kids evade raptors in the kitchen or stare into the beady eye of the Tyrannosaurus.) Just as he had two decades earlier with Jaws, the grandfather of summer blockbusters, Spielberg ushered Hollywood into a new era. Jurassic Park wasn’t the first CGI spectacle—that honor belongs to Terminator 2: Judgment Day, or maybe to James Cameron’s 1989 film, The Abyss—but it was the point of no return for the industry. The modern age of special effects had begun: Now that audiences had seen what computers could do, there was no going back to stop-motion or other outdated alternatives. CGI had rendered them obsolete.

[In 2013], for its 20th anniversary, Universal brought Jurassic Park back to theaters, this time in three dimensions. The 3-D was superfluous—did the T. rex really need to get closer in the rearview mirror?—but it was still thrilling to see Spielberg’s glorified monster movie in a theater again, to hear John Williams’ rousing theme in Dolby surround and see Nedry get his just desserts on a 30-by-70-foot screen. Today, Jurassic Park still feels like the quintessential special-effects movie. The pacing may feel more sluggish and the continuity errors may be more obvious in hindsight, but time has scarcely eroded the movie’s visual pleasures. It’s not that they haven’t aged; one look at the leathery skin of that first dino reminds you how far CGI has come, at least in terms of texture and detail. It’s that Spielberg, more than just about any of his contemporaries, understands that the key to believable effects is the way they’re integrated into the physical reality of the movie. Part of that is having actors like Neill and Dern, who can express a credible sense of wonder when staring into nothingness (or a green screen). But it’s also about using CGI as a solution, not a crutch.

Most of the dinosaurs in Jurassic Park are brought to life by a combination of animatronics and CGI. The famous assault-on-the-jeep scene, for example, cuts frequently (and rather seamlessly) between a giant, robotic T. rex and a computer-generated one, with the latter employed during shots of the animal walking or running. Whenever possible, Spielberg uses the robot, because it has actual weight and dimension; there’s a physicality to animatronics—which occupy real space in the frame, have to be lit, etc.—that CGI can’t quite mimic, even today. The director also proves adept at combining practical and digital effects in a single shot: When the electric fence or an overturned jeep buckles under the weight of the T. rex, only the dinosaur is “not there.” Likewise, when the same imaginary creature throws a different imaginary creature into the skeleton at the end of the movie, the skeleton is actually, physically collapsing into pieces. This moment may work as a striking metaphor for the way Jurassic Park changed the special-effects industry—a “fake” giant destroys the bones of a “real” one—but it also demonstrates how convincing CGI can look when incorporated into an analog-effects setup.

Spielberg, in short, used CGI when he had to, in order to get a shot or image he otherwise couldn’t. In Jurassic Park, perhaps the most influential of all CGI movies, CGI is a supplement—an amazing, cutting-edge supplement, but a supplement all the same. Unfortunately, that was a lesson largely lost on the filmmakers who walked in the director’s footsteps. What was, in Spielberg’s hands, a tool for realizing the impossible quickly became a way to achieve the merely arduous. Why go through the dangerous, difficult, and time-consuming process of flipping a real automobile when you can simply create the same effect using a computer? Well, because the results end up looking like this.

Few things age faster, and less flatteringly, than CGI, which is why many of the once jaw-dropping event movies of the ’90s now look hopelessly dated, even laughable. The fatal flaw of a film like Roland Emmerich’s Godzilla, which came out five years after Jurassic Park, is that it treats CGI as if it’s the whole show, putting the latest advances in technology front and center. While Spielberg’s movie isn’t exactly shy about showing off its state-of-the-art creations—there are more than 50 CGI shots in the film—it also isn’t afraid to rely on implication from time to time. Think of how it builds up the raptors: Their first attack, in the opening scene, essentially happens off-camera; later, when the visitors watch the “clever girls” feast, Spielberg suggests their presence through fearsome audio and shaking foliage. We believe in the raptors, and their ferocity, before we even see them, which makes it much easier, even today, to be afraid of a beast made from ones and zeroes. Same goes for the T. rex, whose power is foreshadowed by one of the film’s most simply achieved effects: the rippling water in the glass, accomplished through nothing more than a plucked, concealed guitar string. If Spielberg learned anything from Jaws—and his malfunctioning robot shark—it’s that not showing the monster can make the scenes where you do show it all the more effective.

It helps, too, that Spielberg knew how to film his dinosaurs, framing them in inventive ways and coming up with cool things for them to do. Today’s money can buy a better dinosaur, but can it buy a better jolt than the raptor leaping right at the camera, narrowly missing the leg of a dangling preteen, or a better gag than “objects in mirror are closer than they appear”? Spielberg and the wizards at Industrial Light & Magic thought about the ways these phony organisms would interact with the real world around them, digitally inserting footage, for example, of splashing puddles where the T. rex steps. Compare that to the stampede scene in Peter Jackson’s King Kong remake, which finds the humans and the dinosaurs often occupying the same physical space at the same time.

Speaking of Peter Jackson, he’s one of several blockbuster filmmakers who have become overly reliant on CGI in recent years, despite an earlier preference for at least some practical effects. His original Lords Of The Rings trilogy stands proudly among the great special-effects achievements since Jurassic Park, largely because it uses a variety of different techniques to bring Middle-earth, and its numerous characters and creatures, to life. Just 10 years later, however, Jackson eschewed that strategy with The Hobbit, replacing intricate miniatures with flat digital cityscapes and amazing prosthetic monsters with more CGI. The reality of Middle-earth, a place that once had an organic quality, was lost in the conversion. James Cameron, another former special-effects omnivore, has all but abandoned tactile effects: While his Titanic plunged audiences into a physical environment, acclimating them to the space before using computers to split it in half, there’s scarcely a single shot in Avatar that doesn’t feature CGI. And let’s not even start with George Lucas’ galaxy far, far away, which used to be cluttered with clunky, rustic, tangible stuff, but was reduced in the Star Wars prequels to a pre-rendered video-game background.

By stripping away all real elements—including, in many recent cases, actual human beings—today’s special-effects showcases fail to create the illusion of, well, reality. That may well be the key to Jurassic Park’s enduring magic: The dinos look a little less convincing than they used to, but the physical world they’re interacting with is really there, so it’s still easy to suspend your disbelief. And there’s probably an element of nostalgia at play, too. Movies can now show audiences just about anything; there’s little thrill left in seeing an alien world or a city reduced to embers, because Hollywood delivers these attractions every single summer. (By contrast, we don’t always get to see astronauts floating in space from every conceivable angle, which is why Gravity has done so well this year.) For viewers old enough to remember their first big-screen glimpse of Spielberg’s dinosaurs, returning to Jurassic Park is like returning to a simpler time, when blockbusters could still shock and awe, and when CGI still felt thrillingly new. That might have been just two decades ago, but it feels more like 65 million years have passed.