Setting
New York City in 1984
Big Bad Apple
WINSTON: I love this town!
Winston says this in one of movie's last lines—this even though he's just spent a New York evening battling a demonic marshmallow man and is still doused in demon marshmallow goop.
The truth is that in 1984, when Ghostbusters first hit the screens, most Americans probably wouldn't have been all that surprised to hear that NYC was full ghosts and demons. It was common knowledge that New York was a total horror show, filthy and infested with crime.
Though Middle America's Big-Apple-phobia was a little overblown, there was no doubt that the city was suffering. The economic hardship of the 70's had hit NYC hard, and it really had gone downhill.
When Egon describes the downtown neighborhood where Ghostbusters HQ is located as "like a demilitarized zone" it's probably not all that much of an exaggeration. Certain neighborhoods were seriously rundown and decaying, and the city had definitely earned its reputation for urban blight.
NY Valentine
So if NYC was such a hole, why did Ivan Reitman push Aykroyd and Ramis to set the movie there? A recent Vanity Fair article quoted the director/producer as saying "I wanted the film to be… my New York movie."
Apparently, it didn't take much convincing. In the same article, Aykroyd says, "It's the greatest city in the world, an architectural masterpiece. [...] energy central for human behavior."
Seems like to the dudes behind Ghostbusters, New York was still an awesome town, and the movie works as a valentine to the city. Tons of NYC landmarks are used as locations in the film. The NY Public Library, Columbia University, Rockefeller Center, Columbus Circle, Central Park, Tavern on the Green, and the towering, upscale apartment buildings of the Upper West Side. Some say Ghostbusters was one of the first movies in the 80's to say that it was okay to like New York again.
Bad Is Good
Even though the filmmakers chose NYC because they had a total crush on it, the movie doesn't hesitate to nod toward the bad stuff about the city and use it to the film's advantage.
Egon tells us that Ivo Shandor's Gozer cult had decided that, "society was too sick to survive," and to most Americans NYC was a symbol of society's sickness. With an underworld of crime, drugs, and violence happening alongside the decadent excesses of Wall Street, the Big Apple represented all that was rotten in the USA.
In the end, though, the movie shows New York united against its common enemy, with tons of New Yorkers chanting for their chosen heroes, the Ghostbusters. As Ghostbusters emerge triumphant after banishing Gozer, we don't see a New York divided and fighting against itself. We see a NYC united and celebrating its survival.
With Winston's great big declaration of love for NYC at the end, it's like the movie is saying, "Yeah, the City has some giant marshmallow-man-sized problems, but it's still an amazing place to be."