A dozen years after the juggernaut that was 1997’s Titanic, writer/director/producer/self-proclaimed “King of the World” James Cameron returns to the cinema of blockbuster action, technical effects and mega-sized budgets and marketing campaigns that he helped ramp up back in the ’80s with The Terminator, T2 and Aliens. Avatar, the picture in question, is rumored to have cost $300 million, with an estimated $150 million in promotion costs. Five years in the making, shot in 3-D in motion capture mixed with live action, this movie (which is almost three hours long) finds Cameron back in sci-fi epic territory, his genre of choice.

Like Titanic, the picture has been the subject of intense pre-scrutiny with critics, bloggers and the general public. Many of the initial reviews have been hosannas. Based on the technical bravura that Cameron once again wields, Avatar is indeed a breathtaking journey into a self-created world. But compelling story? Memorable characters? Unique set pieces? Something/anything to get excited about beyond the technical wizardry as it goes into its long last section? Not really.

Although the movie is entertaining enough and stunning to look at Avatar is essentially an exceedingly detailed three-hour video game—without the benefit of remote controls to mute the dialogue that makes one wince and kill off the annoying cartoon villains hours before Cameron deigns to.

Avatar is based on Cameron’s original script. It’s set on the planet Pandora, a place as lush, mysterious and beautiful as the rainforests of the Amazon but filled with deadly flora and fauna, monstrous creatures and a race of indigenous primitives who hate the human invaders and kill them on sight. These “primitives”—known as the Na’vi—resemble humans but are extremely tall; have blue skin and feline noses; and can communicate with the plant life and other creatures with the feelers embedded in their tails. They speak in their own language, are fierce warriors who live in the great tree in the middle of the forested planet.

Meanwhile, the piggish people of Earth have run out of oil and are now dependent on a natural resource known as—I kid you not—”unobtanium.” And just wouldn’t you know it? There are huge deposits of the stuff right beneath the great tree where the Na’vi are living. The big-money interests in charge of drilling out the stuff, headed in the personage of Giovanni Ribisi as the standard corporate villain, have joined forces with the military to learn the best way to get at the unobtanium.

One plan involves scientifically bonding humans with the Na’vi via one of those virtual-reality chambers, thereby infiltrating their culture on the inside as “avatars.” Sigourney Weaver plays Grace, the chain-smoking head of the science division who wants to coexist peacefully with the Na’vi and their exotic world (she’s got an avatar too) and has no inkling of the corporation/military’s true intentions. She unwillingly takes on Jake Sully (played by Sam Worthington), a paraplegic soldier whose DNA is a match with his late brother, a scientist trained for the infiltration program.

Once Jake transforms into a Na’vi there’s no stopping him, and after encountering the fetching and fearless Neytiri (Zoe Saldana), daughter of the tribal leader, he’s all for some human-Na’vi interaction. (We are spared their coupling.) But Jake hasn’t been completely honest with Neytiri or her people: He’s actually collecting intel for the evil Colonel Quaritch (Stephen Lang), head of the military operation, so the military can figure out the Na’vi’s weak spots. The creepy Quaritch, who seems to favor spray-tanning and seems to only wear muscle T-shirts, has promised Jake that the military will pay for an expensive operation to restore his useless legs if the intel is good (and there’s also a decidedly homoerotic undertone in his clenched-jaw encounters with the handsome Jake).

Everything seems to be going hunky-dory until Jake becomes enlightened and he falls for Nytiri, her people and their way of life, and turns on Quaritch. Then, natch, there’s hell to pay. Up to this point, the picture has been breathtaking too look at as the story has meandered along entertainingly enough. The long, long movie moves at this point from one not-particularly-involving action set piece after another, and the usual plot reverses.

But that doesn’t lessen its visual impact. And, to be sure, it is in the visual department that the movie works best (and is it’s only real triumph). With Avatar, Cameron has again proved that he’s a master at marshalling the forces of movie technology to realize his dreams. But he should learn to collaborate in the script department. Cameron’s bold vision and immense directing gifts have wrought a visual masterwork—but Avatar sits atop the very thin precipice that is his facility with the spoken word—and that will be its lasting, fractured legacy.