Stars Sam Neill, Laura Dern, Jeff Goldblum, Richard Attenborough. Directed by Steven Spielberg. Screenplay by David Koepp, adapted from the Michael Crichton novel. 127 minutes. Rated PG-13. Critic’s grade: A-

There are two or three things we already knew about “Jurassic Park 3D,” even before going to see the retrofitted blockbuster, the hugely successful Steven Spielberg-directed scary dinosaur movie.

First, although it’s been juiced with a 3-D Imax restoration, there’s no genuine artistic raison d’etre for the sci-fi thriller, spiked with elements of horror as well as comedy. No additional footage is on offer — this is no “director’s cut.”

Secondly, its return is tied to a tidy anniversary, as it’s been 20 years since audiences were first frightened by the then-innovative CG sight of the enormous prehistoric beasts, surprisingly realistic looking (at the time) and sprung right out of Michael Crichton’s imaginative bestselling novel of the same name.

So, then, Spielberg’s flick, built around a concept — genetic cloning could make it possible to recreate the Tyrannosaurus rex and his species mates — that once seemed vaguely possible, was largely brought back because of the opportunity to sell it to a new generation of filmgoers.

And, as a bonus, it helps boost younger audiences’ interest in the forthcoming “Jurassic Park 4,” directed by Colin Treverrow and reportedly  featuring a new addition to the menagerie of dinosaurs seen in the original flick and its two successors (as of now, the film is slated for release in summer 2014).

Win-win, right? Particularly at the box office.

And yet, and yet, there’s more to it than that.

Two decades later, and with the benefit of 3-D technology that indeed lets viewers feel as if they’re right in there, fleeing from the enormous, lumbering T Rex and the speedy,  razor-toothed velociraptors, the first film in the “Jurassic Park” franchise retains its power to give chills and thrills to audiences.

Put simply, the movie’s re-emergence offers longtime fans the chance to watch the modern movie classic again  on the big screen, clearly the natural habitat for this type of film. It also provides the same opportunity for younger audiences who’ve never had that privilege, like the shocked and awed teenagers (my kids and their friends) who attended the screening with me.

Right away, the visuals prove stunning, as kindly mad scientist/entrepreneur John Hammond (Richard Attenborough) brings a helicopter full of scientists to “the most advanced amusement park in the world,” as Hammond describes it. The green, green hills of the island, near Costa Rica (actually, Hawaii), look more lush than ever, and the soaring waterfall sparkles. It’s a great start for a big adventure.

Of course, all that pales in comparison with the first time that serious-minded paleontologist Alan Grant (Sam Neill), his partner in dino fascination Dr. Ellie Sattler (Laura Dern) and flirtatious, uh, chaos theorist Dr. Ian Malcolm (Jeff Goldlum in his prime, all swagger and wisecracking fun) lay their eyes on the park’s star inhabitants.

Spielberg, justifiably celebrated for his work directing last year’s Oscar-winning historical epic “Lincoln,” was still making popcorn movies in the early ’90s.

And there’s enormous fun to be had — lots of frights, a surprising number of laughs — as Hammond, his two too-cute grandchildren, the scientists and characters played by Wayne Knight (“Seinfeld”) and Samuel L. Jackson, then still a second-string player, get to know and then attempt to escape the prehistoric monsters.

Remember the huge pile of dino dung? The T. rex’s attack on the SUVs? The raptors’ pursuit of the kids, in the welcome center’s kitchen? The terrible fate of the thieving IT guy (Knight)? They were awesome then, and still are.

“Creation is an act of sheer will,” Hammond says at one point, bragging about the ingenuity and determination it took to engineer a revival of the time when dinosaurs walked the earth.

Sheer will, too, with an eye on considerable commercial prospects, was required to revive “Jurassic Park 3” for a theatrical run. Glad that Spielberg made the effort.