There are big movies, and then there are BIG movies.  James Cameron’s technical chef d’oeuvre and decade-long undertaking, “Avatar,” is neither — it’s bigger.  It occupies a category of colossal movie-making so unspeakably behemothic that taxonomy itself may take years to catch up.  From the same director who gave us “Terminator 2: Judgment Day,” and “Titanic,” both the most expensive films of their time, and with a budget somewhere in the ballpark of $4oo million, I suppose nothing less than sheer grandeur and cutting-edge spectacle should have been expected.

But considering its admittedly impressive technical achievements, some see “Avatar” as more than merely an astonishing visual experience.  Its revolutionary employment of performance capture CGI technology has been compared to the first enchanted moments of synchronized audio in 1927′s “The Jazz Singer,” or to the innovative usage of Technicolor in pictures like “The Wizard of Oz” or “Gone With the Wind.”  And from a purely methodological perspective, it’s hard to argue with those comparisons.  Throughout my screening I repeatedly leaned over to the person next to me to whisper, “Can you believe that’s computer imaging?!”

Cameron, astoundingly, has managed to sidestep, or rather build an incredibly expensive bridge across the Uncanny Valley of human likeness that has devoured all of Robert Zemeckis’ motion capture endeavors, notably “The Polar Express,” and “Beowulf.”  “Avatar” unquestionably represents a watershed moment in the advancement of technical filmmaking.  But film is a multi-faceted, dynamic art form that requires a number of elements to work in concert to produce a fluid work of substantial merit.

What about “Avatar’s” narrative, direction, performances, score, pacing, editing and even morals?  The three revolutionary films mentioned above aren’t canonized merely for advancing the technology of filmmaking.  All are sound and complete entities and have appeared on various reputable lists of the greatest films ever made, an honor James Cameron’s magnum opus could never dream of being awarded.  It seems Cameron has decided not only that bigger is better, but that big is the only game in town — character development, narrative integrity and good writing be damned.

The acting is atrocious.  Sam Worthington, who was the best thing about the otherwise insufferable “Terminator Salvation,” is flat and uninteresting here.  And his American accent needs a lot of work which only compounds the problem of his relentless, tiresome and utterly unnecessary narration.  One of Hollywood’s most consistent and reliable supporting players, Giovanni Ribisi (“Saving Private Ryan,” “Lost in Translation”), delivers a laughably caricatured characterization as the malevolent business-monger, Parker Selfridge. The generally riveting Sigourney Weaver is reduced to nothing more than a cardboard cutout spouting platitudes as the unsubtly named, Grace Augustine.  And the walking cliché, hard-nosed Colonel Quaritch, played by Stephen Lang (“Gettysburg,” “Tombstone”), may just be the most banal, least nuanced film character of the decade.  Ironically, Neytiri, the giant blue alien played by Zoe Saldana (“Star Trek”), is the only sympathetic and recognizably human character in the entire film.

Perhaps “Avatar’s” most egregious deficiency, however, and the most likely culprit for the ungodly performances, lies with the script.  Do we really need to hear another movie character utter the words, “You are not in Kansas anymore,” ever again?  After a decade of mulling over this script, it’s hard to believe Cameron still couldn’t avoid the most elementary pitfalls of screenwriting.  The little rock the American mercenaries are after is literally named “unobtanium” for crying out loud!  But Cameron is no dummy.  He’s a socially conscious auteur capable of crafting genuinely compelling art.  “Avatar” is loaded with references to current events and oozes anti-war, anti-Bush, anti-imperialism, pro-environment sentiments, which is terrific.  Good art should not only be an effigy of the state of society, but comment on it.  “Avatar” certainly does that, but in such a pedestrian, boorish way that its messages are all but rendered impotent.  Does Cameron really think his audience needs to hear the words, “Shock and Awe” to make the already obvious connection to Operation Iraqi Freedom?

So “Avatar” is crucially flawed.  But is it fun?  You bet it is.  It’s one helluva good time.  Although it’s an uneven amalgamation of “Dances With Wolves,” “Braveheart,” “Lord of the Rings,” and Cameron’s own “Titanic,” and fails to live up to any of them, “Avatar” still manages to dazzle in delightful and unexpected ways sure to leave even the most skeptical viewers awestruck, at least superficially.  The visual experience is that good.  Cameron was clearly determined to turn the world of visual effects on its head, a goal he’s more than achieved.  But he’s left a paramount casualty in good storytelling in his $400 million wake.