Computer-generated aliens of Men in Black II dazzle with their inhuman feats. Spider-Man's digital double swings among skyscrapers at breakneck speed. And the CGI Yoda in Star Wars: Attack of the Clones stages a fight the original puppet never could have managed.

MIB II, which opens July 3, is just the latest in a litany of movies that rely heavily on digital special effects. One such film, Scooby-Doo, features a completely virtual dog as the lead character.

Many filmgoers are impressed with the modern film effects, of course. But others have adopted Scrooge's "Bah, humbug" attitude about the new technology.

"I think all special effects look fake now," said Charles Taylor, a movie critic and contributing writer for Salon.com. "Special effects are there to be noticed, and they tend to throw me out of the movie."

Film critic Roger Ebert took issue with the CGI sequences in Spider-Man.

"When you see Spider-Man flying through the sky and leaping between buildings, he looks like an artificial cartoon character," Ebert, who gave the blockbuster a "thumbs-down," said in a review. "He moves too fast, without the weight and presence of flesh and blood."

Digital animation and computer-generated imaging have revolutionized the special effects in movies. The models, puppets, wires and painted backgrounds once used have all but vanished. Even body doubles are becoming obsolete.

"It's really diminished the role of stuntmen," Taylor said. "You don't get to see people do these crazy things anymore."

Some people are nostalgic for the effects of the past, like the surreal cyclone in The Wizard of Oz, the moving screens that created the illusion of driving a car, flying characters with visible suspension wires and scale models used in films like the original Star Wars trilogy.

"You got a feeling of the human hand behind everything," said animator John Canemaker, author of Walt Disney's Nine Old Men and the Art of Animation. "Some of the effects weren't perfected, but there was a charm about it. I miss that human touch."

Canemaker, director of the animation program at New York University's Tisch School of the Arts, characterized the old effects as "clunky," but said they allowed viewers to catch a real glimpse of what went into making those movies.

But he sees a downside to the ways of the past, too.

"Audiences had to work harder to suspend disbelief," he said.

Others believe that aspect of bygone special effects was a good thing.

"If you look at older movies, people had to rely much more on their imagination," Taylor said. "(Modern) movies are reduced to spectacles. That encourages a certain laziness on the part of the audience."

Because they required more imagination, Taylor said, the effects of the past did a better job of drawing viewers into a fantasy land.

And even CGI fans acknowledge that some films today have an artificial quality.

"It does look fake you know it's computerized, not real," said Chien Hwang, an advertising art director in New York.

Though he liked Spider-Man, he said that "you look at it and think it's a video game. I don't buy for a second that it's Tobey Maguire in the suit swinging around. But I appreciate the art."

He and others predict that, eventually, the kinks will be ironed out.

"Digital effects are still in their infancy," said Coury Turczyn, editor of the online PopCult Magazine (www.popcultmag.com). "But they'll improve."

Today's technology has made special effects cheaper and less time-consuming than their predecessors, opening limitless doors for filmmakers.

"They can do literally anything now with special effects," Canemaker said. "The difference between animation and live action has been blurred, and it's no longer easy to tell where reality and fantasy begin and end."

A scene from Jurassic Park in which the actors seemingly run amidst a herd of dinosaurs is a case-in-point, he said.

But digital effects are becoming so spectacular that some movies hinge on them at the expense of plot or character development.

"You can overuse digital effects to the point where they become the main focus of the movie as opposed to the story," said Turczyn. "They provide lots of eye candy, and filmmakers forget you really need a good script on top of that."