Only one of this past weekend's three major new releases performed up to box-office expectations: "Unstoppable," cruising along with stellar critical reviews and two thumbs-up from moviegoers, delivered pretty much what every Denzel Washington/ Tony Scott project does: $23.9 million.

But the low-budget alien-invasion flick "Skyline" and the easy-to-digest rom-com "Morning Glory." both debuted on the low end of B.O. prognostication. The former has been riding a wave of buzz out of Comic-Con this summer, while the latter starred some of the most familiar faces in Hollywood, Harrison Ford and Diane Keaton. So what happened?

For "Skyline," it seems, there was nowhere to go but down after that buzzy Comic-Con teaser trailer. The film, as critical reviews made clear, simply wasn't very good. Universal choose not to screen it in advance, hoping to sneak fans into the theater before negative word of mouth trickled out. And it worked, up to a point.

"Not screening the film in advance allowed Universal to get at least one day of sales in before bad buzz kicked in," said Gitesh Pandya, editor of BoxOfficeGuru.com. "Opening day accounted for a whopping 41 percent of the entire weekend gross, so they did what they had to do given the weak product."

The fanboy community was already on high alert about the film, based on the directors' prior work, the endlessly mocked "Aliens vs. Predator: Requiem." Once bad buzz on "Skyline" started to seep out Friday — it scored an embarrassing D- grade from audiences, according to CinemaScore — there was no hope for the flick to boost its gross. In the end, despite its initial hype and comparisons to everything from "District 9" to "Paranormal Activity," moviegoers recognized a generic alien-invasion flick when they saw it — or, as it were, didn't see it. Even "The Fourth Kind," which barely scratched the pop-culture consciousness last November, outgrossed "Skyline."

"It ended up being the only film to see sales drop from Friday to Saturday," Pandya pointed out.

"Morning Glory," meanwhile, had the benefit of a massive PR effort and those ultra-recognizable faces in Ford, Keaton and Rachel McAdams. But the film suffered from poor reviews and an inability to distinguish itself from what Pandya called "the same generic single-gal-juggles-career-and-love-in-the-big-city genre."

Keaton has never been a big box-office draw, and save for the latest "Indiana Jones" flick, Ford hasn't had a hit in more than a decade. "What's most disappointing about 'Morning Glory' is that after 15 years without a comedy, Ford's turn in this, something more spry, was supposed to get him back to his crowd-pleasing ways," Steven Zeitchik wrote in the Los Angeles Times. "But the movie's disappointing performance adds one more nail in a coffin that's been enveloping Ford's career, 'Buried'-style, for years."

Yet according to Paramount, 89 percent of the film's audience was older than 25, and BoxOffice.com editor Phil Contrino suspects "Morning Glory" might hold up in the weeks ahead.

"I'm not quite ready to write this film off as a disappointment," Contrino said. "I think it's going to show healthy staying power in the weeks to come. It's skewing older, so that means the audience it appeals to doesn't feel the need to necessarily rush out during the opening weekend. It's a funny movie with plenty of pep, and I think a lot of moviegoers will still discover it."

Check out everything we've got on "Skyline" and "Morning Glory."

For breaking news, celebrity columns, humor and more — updated around the clock — visit MTVMoviesBlog.com.