Invited guests watch the film "Black Panther" in 3D which featuring Oscar-winning Mexico born Kenyan actress Lupita Nyongo during Movie Jabbers Black Panther Cosplay Screening in Nairobi, Kenya, on February 14, 2018. YASUYOSHI CHIBA | AFP | Getty Images

If the only showing available for Disney's "Avengers: Endgame" was in 3D, would you pay to see it or wait a week to watch it in 2D? That's the question many Marvel fans are facing as we reach the opening weekend of the hotly anticipated superhero flick. As theaters fill up, single seats and tickets to 3D showings are some of the only options for moviegoers who haven't purchased tickets yet.

While there was a resurgence of 3D films in the early 2000s, popularity for these movies has declined dramatically over the last two decades, particularly in the U.S. In 2018, tickets to 3D screenings accounted for about 16% of the global box office, hauling in around $6.7 billion. This was a decrease of 20% compared with 2017, according to an annual report from the Motion Picture Association of America. In the U.S., 3D wide releases decreased 21% over 2017, the MPAA reported.

"Studios used to report the 3D percentage in the opening weekend tell-all and they rarely do that now, because there is no reason to report it because it's so dismal," said Jeff Bock, senior analyst at Exhibitor Relations. Once considered pure spectacle, 3D has lost its luster with audiences. Not only are the plastic glasses uncomfortable, but the 3D elements aren't always purposeful. In many cases, the technology is an afterthought and the films are converted to a 3D version in post production. "Nobody is shooting exclusively in 3D, except for maybe James Cameron with 'Avatar,'" Bock said. "When 'Avatar 2' comes out people probably will go see that in 3D because it was made for 3D." For films that aren't produced with 3D as a priority, the foreground images remain crisp and pop during the viewing, but the background tends to get blurred and out of focus. For this reason, many moviegoers consider 3D to be more of a distraction than an experience. Kids, of course, are more enthusiastic about 3D films. On average, 7% of this group cited 3D as the reason they wanted to see a film, according to Comscore's PostTrak audience survey. For comparison, around 4% of parents and 3% of general audiences cited 3D as the reason to see a film. Paul Dergarabedian, senior analyst at Comscore, noted that the success of 3D is very content-centric. Meaning certain films fare better than others when it comes to 3D showings. For example, 22% of kids said that they wanted to see "The Angry Birds Movie" because of 3D, 12% of parents said they wanted to see "The Crimes of Grindelwald" for the 3D, and 14% of general movie audiences wanted to see "Teenage Mutant Ninja Turtles: Out of the Shadows" for this reason.