In the 1980s and into the 1990s, one of the most durable genres in the American cinema was the Big Dumb Fun action movie, empty-calorie exercises in elaborate setpieces and corny one-liners. We still have action movies, of course, and they're still Big and Dumb, but very few of them are any Fun. I blame computers, at least a little bit: when every third shot contains a digital hero instead of a flesh-and blood Chuck Norris/Arnold Schwarzenegger/Steven Seagal/et cetera, the result lacks a certain liveliness. Not to mention, computers have done away with the small, fun action scene; if it doesn't involve twelve locations and at least two speeding trains, it's not good enough any more.

Whatever the reason (and it's not just the rise of CGI, I know), action movies just aren't what they used to be. I bring this up on the release of the second film within a year to bring back the Big Dumb Fun action movie: after Live Free or Die Hard brought one old franchise back for a much-belated fourth entry, Sylvester Stallone's Rambo does the same thing to an action trilogy whose last entry was released nearly 20 years ago. Except, for a Big Dumb Fun action movie, Rambo goes rather far out of its way to avoid being much Fun.

Of course, the cinematic adventures of John Rambo were always a bit too serious for their own good: First Blood, much the best of the series (indeed, the only "good" one in the bunch) was less an action film and more a drama about a disturbed Vietnam vet who can't deal with normal life and lashes out with violence at anyone who crosses him; Rambo: First Blood Part II was a self-conscious attempt to give moderates a psychological victory in 'Nam; Rambo III was at least partially a lesson about the mujahadeen in Afghanistan. While I'm thinking of it, I'd like to call attention for the way that none of the four films in the series have been titled the same way. Must be merry hell for the video store clerks.

Anyway, the first three Rambo films were all semi-serious looks at the Problems Facing The World, mixed-in with fantasies about how much better the world would be if the American military could just whup the hell out of our enemies: the Vietnamese, the Russians, leftists. The curious thing about Rambo is that, while it is still a hawkish wank about how the US should poke our nose in everybody's business, it's specifically a call to American intervention in Burma. Burma? That's not, let us say, high on the list of places that Average American Filmgoer thinks about when the dinner table conversation turns to interventionism. So it's not, like the others, a bit of red meat for neocons. It's an attempt to educate the US on the terrible state of a far-away country, and while I applaud the intent, a Big Dumb Fun movie can't be dumb and won't be fun if it's actually meant to work as a political call to action.

As such, it opens with a short montage of news footage (most of it British), documenting the atrocities committed by the Burmese government against the Karen rebels, a Christian community. Later on, the film depicts the savage destruction of a village full of farmers and missionaries, a sequence directed with considerable skill and exactly the correct amount of restraint: we see just enough of every violent act to make it clear what happened (and some of it is the stuff of nightmares - a baby thrown into a bonfire, for instance), but never does the camera linger over the blood and devastation. It's just about the best scene Stallone has ever directed, and a good sequence by any yardstick, visceral and hard to forget.

That "hard to forget" is the problem. Every Rambo film has to negotiate the same turn about one-third of the way through: how to go from a geo-political piece to a "blowing shit up good" piece. In the first sequel, this is achieved by essentially resetting the whole plot; in the second sequel, this is achieved by having the first act make no sense at all, so that the audience has no preconceptions.

In Rambo, the goal is clearly to negotiate that shift by changing the plot around: in Act I, John Rambo, now living in seclusion in the jungles of Thailand, brings a group of prayer-book toting American Christians to Karen territory, in Act II he brings a group of mercenaries to Karen territory to rescue the Americans, in a government camp. But where Rambo: First Blood Part II and Rambo III used the real world as a pretext, Rambo has done such a bang up job of convincing the audience that the situation in Burma is the closest thing to Hell on Earth, it's basically impossible to forget all that and enjoy the copious action that follows. The very brutal violence that opens the film casts a pall over the very movie-fake violence that follows.

Which is a bit of a shame, because some of that fake violence isn't half bad: certainly better than the hectic and confusing finale of Rambo III, and blessed with the escalating absurdity of a real '80s action picture, particularly in the moment when Rambo explodes what is probably not a nuclear device, but which has the ability to level a couple square miles of forest. Fountains of the red stuff spew with satisfying regularity, and Stallone, though clearly older, has lost none of the skills that made him work in the role to begin with: large muscles and a threatening monotone. It doesn't make the action look as effortless as the fourth Die Hard did - the CGI is obvious - but it's fun enough as a simple guilty pleasure, and perhaps the best straight-up mayhem the series has offered, what with the superior first film lacking much ultraviolence and the first sequel sputtering in between setpieces.

But for all that, it's just too hard to get into it: the beginning of the film sets the wrong tone altogether. It's a guilty pleasure all right, and one that puts extra emphasis on the guilt. Maybe this was the point - maybe Stallone was consciously working to point out the danger of rooting for movie violence in a violent world. But the last act doesn't read that way: it's as rousing as can be, with all the proper moments of death shot and edited to demand cheers and applause.

It was just 13 months ago that Stallone brought another long-dormant franchise out of mothballs, turning in the best film in the series since the first, but the Rambo movies were never as good as the Rocky movies, and Rocky Balboa is an entirely different animal than Rambo, raising questions of aging and the very idea of reviving that which did not need revival. Rambo is just a big dumb action movie, and while it has the right ingredients to be good enough, it sabotages itself too much to click. It's much better than we had any right to expect, but "a great Rambo" movie is still faint praise, and Rambo leaves a taste much more sour than exhilarating.