Rest assured that most voices will be raised in praise of “Star Wars III: Revenge of the Sith.” When they first appeared, the same was true of “The Phantom Menace” and “Attack of the Clones.” Over time, of course, opinion on those previous installments in the series nosedived, and the same is likely to happen with this last picture in George Lucas’ second trilogy, too. The sad fact is that although “Sith” is leagues better than either “Menace” or “Clones,” and even an improvement on 1983’s “Return of the Jedi” (the fact that it contains no Ewoks and only a fleeting glimpse of Jar Jar Binks alone would almost guarantee that), it doesn’t approach the quality of either the first “Star Wars” movie, now called Episode IV and subtitled “A New Hope,” or “The Empire Strikes Back,” which is certainly the highpoint of the series. Technically magnificent but dramatically inert, it’s a lumberingly predictable finale to the space saga that peaked in 1980 and has been going downhill ever since. If you plotted the entire “Star Wars” phenomenon on a sort of earnings graph (calculating excellence as opposed to boxoffice receipts, of course), you’d have a line that starts off high in 1977 and shoots into the stratosphere with “Empire,” but declines precipitously with “Jedi” and sinks deep into the black with “Menace” and “Clones,” only to spike upward with “Sith”–but not quite enough to get back into positive territory. And that’s just not good enough.

A major problem with the movie, of course, is that its narrative course is pretty much predetermined: to get to the beginning of “A New Hope,” it must basically explain how Anakin Skywalker (Hayden Christensen), the protégé of Jedi Obi Wan Kenobi (Ewan McGregor), turns, under the malignant influence of Grand Chancellor Palpatine (Ian McDiarmid), to the Dark Side of The Force and becomes Darth Vader. Not-so-side issues involve how Anakin’s secret wife, Senator Padme (Natalie Portman), comes to bear him twins Luke and Leia, and under what circumstances they’re separated to rediscover each other in future installments; and what becomes of the other characters who will turn up later–Kenobi, of course, but also Yoda (voiced by Frank Oz), the robots C-3PO (Anthony Daniels) and R2-D2 (Kenny Baker), and of course the transformed Palpatine. And there must be explanations about why other characters, like Mace Windu (Samuel L. Jackson) and Count Dooku (Christopher Lee) don’t make it to the next episode.

In constructing his script, Lucas manages to answer all the questions, though without any surprises along the way. He does spotlight a new villain, the crablike General Grievous (a pure CGI creation) and punctuates the story with fights and space battle scenes that are superbly choreographed and beautifully rendered. But quite honestly even light saber combat pales after a while; and while the images of multiple ships engaged in ferocious conflict against a star-pocked sky are incredible, they’re so complex as to be almost impossible to take in from any tactical point of view. (Moreover, the sight has become so familiar in big-budget movies nowadays that even when taken to the next technical level, as it definitely is here, it can’t match the excitement of seeing those mere two vessels at the very beginning of “A New Hope.”)

Still, one can’t seriously complain about the effects in “Revenge of the Sith”–they’re great by any contemporary standard. Where the picture stumbles badly is in the expositional dialogue sequences. True, we’re spared the kind of long-winded disquisitions on trade pacts and economic negotiations that disfigured the most recent installments, and there’s less reliance on CGI-manufactured characters and more on the human beings, which is a good thing. But it would be a lot better if the people were given good lines to speak, and if Lucas utilized the actors in something more than a thoroughly pedestrian way. The franchise creator has never had much of a way with dialogue, of course, nor has he ever been much of a director; “A New Hope” got by with sheer adolescent exuberance, but it’s no accident that the superior “Empire” was written by Leigh Brackett and Lawrence Kasdan and helmed by Irvin Kershner. To his credit, Lucas shows that he’s learned from their example: he’s tried to craft a less juvenile, jargon-laden script than “Menace” and “Clones,” and he seems to be striving for the operatic sweep of “Empire.” But he comes up short in both areas. “Sith” is solemn and serious, but ineffectually so. The dialogue avoids diplomatic drudgery, but it takes melodramatic banality to new levels, especially in the scenes between Anakin and Padme, and Lucas stages the resultant near-campy conversations with a solemnity that’s nearly liturgical. The flaccid, turgid pacing of the more intimate scenes is a sorry contrast to the lickety-split action sequences. (The picture also shortchanges us on humor. There are a few of the customary dabs of that pseudo-heroic jesting that Han Solo specialized in, but they disappear as the plot goes on. We’re left instead with little more than an offhanded reference to one Commander Cody–a name baby-boomers whose memories extend back to the late fifties might enjoy.) The cumulative effect of all this on the cast is very unfortunate. Christensen, who exhibited substantial thespian chops in “Shattered Glass,” is reduced to a smoldering glower for the most part, and his big “conversion” scene is so underwritten, almost elliptical, that it gives him no real opportunity to make the character’s transformation credible (or even explicable). Portman looks even more stranded; though she’s happily been freed of the awful head paraphernalia of “Menace,” she’s asked to do little but make a constant show of deer-in-the-headlights concern for her beloved. McGregor has never managed to make Obi Wan his own, always seeming a pale stand-in for a young Alec Guinness, and while he gets by in the gung-ho fight scenes (one while riding a Ray Harryhausenesque dragon), elsewhere he seems lost, stroking his little beard in imitation of Guinness’ shtick to designate the character. Jackson and Jimmy Smits (as goody-two shoes Senator Organa) mostly stand around trying to appear imposing, though the former does get a dandy light saber combat scene; the veteran Lee is on hand all too briefly. As for McDiarmid, he possesses the vocal suaveness to pull off a seductive villain like Palpatine, but unfortunately in the closing reels he’s reduced to cackling malevolently like the Wicked Witch of the West for protracted periods, never a happy circumstance for an actor of any distinction. In fact, the most praiseworthy performance in “Revenge of the Sith” is given by Yoda, and one has to say that any movie in which the best acting is done by a puppet, however advanced his design, suffers from a lack of directorial skill. Another holdover whose work isn’t at its best is composer John Williams, who recycles the themes from previous episodes efficiently enough until he resorts to choral interjections toward the close–a sure sign of creative desperation.

Still, most viewers will probably be willing to set aside the individual deficiencies of writing and performance to savor the periodic action scenes and the lengthy finale, which first cross-cuts between two elaborate light saber fights and then contrasts the birth of Luke and Leia with that of a much more ominous figure. Though the combat goes on too long, it’s capped by an iconic moment a lot of fans have been waiting to see since 1977 and comes of reasonably well. And even if that doesn’t satisfy you, one can always set aside the predictable plot altogether and just wallow in the state-of-the-art effects, which are spectacular even though they’re curiously circumscribed by a lack of larger context. (Am I the only person who’s bothered by what seems the utter vacuity of the society that surrounds the political-military elite at center stage here? We see them interacting within a gargantuan city against a sky that’s constantly filled with luminous flying ships, but there’s never any indication where anyone else might actually be going. The only entertainment venue we ever see is a big auditorium–perhaps the Senate chamber itself–in which huge, shimmering balloons bounce about to glum reactions from the observers. If this represents the culture of the Republic, maybe Palpatine is right and it deserves to die. The show appears to be considerably less inventive and amusing than even this movie.)

There is, to be sure, one aspect of “Sith” that has real resonance–but one wonders whether most viewers will even notice it, let alone embrace it. That’s the way in which the anguished Skywalker justifies his actions after his seduction to the Dark Side by the notorious Darth Sidious. “Whoever isn’t with me is my enemy,” he shouts. The similarity to the words our own president used in challenging the world to join him in his battle against terrorism–“Whoever isn’t with us is against us”–can hardly be accidental. Later, Obi Wan criticizes the young traitor for seeing things in absolutist terms. Sound familiar? And then there’s the scene in which the republican Senate willingly votes much of its authority away to Palpatine in the state of emergency that he claims exists. It may hearken back to the German Reichstag’s grant of its power to the new chancellor, Adolf Hitler, in 1933, but can’t it also be read as a reflection of the way in which our current executive has usurped much of Congress’ power? There’s a certain glee in reading the final installment in the “Star Wars” saga as an anti-Bush diatribe, a sort of warning against crypto-fascism. But even if that’s George Lucas’ intention, it’s unlikely the message will reach many ears in his audience, or please them if it does.

No, “Revenge of the Sith” will be taken by most as nothing more than the long-awaited last act in a saga they’ve lived with since the days of Jimmy Carter, the picture that ties everything together in pretty much the way they expected and wanted. And while it’s moderately successful taken simply on that level, it could have been–as the first two installments demonstrate–much more. So despite its visual splendor, as the syntactically challenged Yoda might say, to the series “Sith” an entirely worthy capstone is not.

But money-wise, it will still be a smash.