"Once Upon a Time in Mexico" isn't terrible, but it should be much better than it is. It has most of the ingredients of a good action film: a capable director, a bevy of talented, handsome A-list actors, and plenty of opportunities to blow shit up. It also features clever dialogue, an exciting soundtrack and beautiful cinematography. Most of this comes thanks to Robert Rodriguez. He not only wrote and directed, but also "shot, cropped and scored" the film, according to the closing credits. He does a fine job with all of it, but the movie still falls short.

There's tons of plot, but it makes little to no sense. It's more of an excuse for everyone to pull off neat tricks and deliver quirky lines. This makes for an uneven movie that has plenty of shining moments, but is rather dull the rest of the time.

From what I understood, El Mariachi (Antonio Banderas), the legendary hitman hero of "Desperado," has isolated himself and given up his dangerous trade. Along comes Sands, the CIA agent (Johnny Depp) who wants to "restore balance to Mexico" by convincing El Mariachi to come back and kill Marquez (Gerardo Vigil) after he stops Barillo (Willem Dafoe) from assassinating the Mexican president (Pedro Armendariz). El Mariachi-also known simply as "El," as in "the," takes the job in order to get revenge on Marquez, who caused the events leading to El Mariachi's self-imposed exile.

It sounds simple enough, but the story takes dizzying twists and turns. Several other characters are thrown into the mix, including El's gorgeous wife (Salma Hayek), a dangerously sexy federal agent (Eva Mendes), a retired FBI man (Ruben Blades), and Barillo's Chihuahua-loving lackey (Mickey Rourke).

The characters are one of the movie's strongest points. Any one of the main characters in "Mexico" has more personality than the entire cast of "XXX" put together, and the actors fill out their roles skillfully. Banderas spends quite a bit of time brooding, but he does so very attractively, and he and Hayek have more smoldering chemistry than any other on-screen couple in recent memory. Dafoe, Rourke and Vigil are entertaining in their respective roles as creepy, funny and scary.

But to anyone who has seen this summer's "Pirates of the Caribbean," it should come as no surprise that Johnny Depp is the standout, illuminating every scene he's in. Sands is simultaneously determined, eccentric, cheeky, chilling, funny and just on the other side of crazy. "Restoring the balance," for him, involves saving the president, yes, but also killing the cook because the food he makes is too good. Sands wears cheesy tee shirts with slogans like "C.I.A.: Cleavage Inspection Agency" (Depp's choice), carries around a fake arm and says things like "Are you a Mexi-CAN or a Mexi-CAN'T?"

It's too bad, then, that each character, including Sands, seems to be in the movie for a total of 10 minutes. Actually, Banderas is in it for much longer than that, but his scenes are strangely unsatisfactory-which is the movie's fault, not his. Even though he's involved in most of the exciting action sequences, it still felt to me like he didn't have enough to do. Since there are so many characters, we don't learn as much about each individual one as we'd like to, which makes it harder to care about them. Certainly it would be a shame to get rid of any of these interesting characters but if cutting Mendes's role meant getting more of Depp, I would have been all for it.

The action scenes, though skillfully choreographed and shot, can also get to be too much. They start off as fun but outstay their welcome. In one scene, El Mariachi and several other men start shooting at each other in the church. So far, so good. But apparently a church fight scene must end in complete destruction, and that takes a while. By the end of the scene, I was getting impatient for the next one. Fortunately, this is not always the case. One scene in particular, a flashback involving Banderas, Hayek, Vigil and plenty of guns and knives, hits the perfect level of intensity. It ends just early enough to make us hope for more and just late enough to gratify us for the time being. However, "Mexico" is fundamentally an action movie, and if most of the action isn't that enjoyable anyway, what's left?

Don't get me wrong. "Mexico" is an excellent film in many ways, most notably in terms of sight and sound. The dusty Mexican streets make for a hauntingly beautiful backdrop. The luxurious cinematography lets us take in and appreciate what's going on, whether it's a quiet moment in bed or a violent scene in a bar. The Mexican-flavored soundtrack complements the action and gets blood flowing at all the right moments. Nor does it hurt that the actors are good-looking and the dialogue witty.

It's just that ultimately, the film could stand to be a little less ambitious and a little more enjoyable. I'm not sure whether I wish "Mexico" were longer, so that there would be room for all the excess baggage, or shorter, so that there wouldn't be so much to begin with. Either way, I wish it were more streamlined. Maybe next time, Rodriguez will set lower goals and actually reach them. We might get less of everything, but the final product would probably be more satisfying.