Typically, a big budget is considered to be the best way to ruin a comedy - Evan Almighty, Land of the Lost, name your own. Ghostbusters is a rarity, a movie that ambitiously seeks to be a whole bunch of different things - raucous comedy, horror film, tentpole adventure movie - and does them all well.
One of the reasons why the movie succeeds so well, for me, is that it clearly takes place in a real world. Even though the movie brings the audience into a world populated not just by ghosts, but ultimately by elder gods out of something written by H.P. Lovecraft, the filmmakers slowly and carefully introduce the different fantastical elements to draw the audience into the fantasy. The production design and cinematography have more in common with the gritty , high-contrast look of a 1970s movie than with the more plastic, shiny tentpole movies that Hollywood would put out later in the decade and up to the preent - basically, the look of this movie is a lot closer to Dog Day Afternoon than Men in Black. So when the Staypuft Marshmallow Man arrives at the movie's climax, it's both ridiculous, but totally embedded into the world of the movie.
As the release of Paranormal Activity shows, spooky things are scarier when they happen in the context of a normal, naturalistic setting. Now, I wouldn't say that Slimer or the other ghosts in this movie are scary for me nowadays, but when I first saw this in theaters at the age of seven, the Library Lady and the Taxi-Driving Ghoul were enough to freak my shit out. And I think it's in no small part because of the naturalistic way the movie presents them.
Of course, this naturalistic production design and cinematography are primarily at the service of letting the comic actors do their thing, and the bulk of the movie is about giving Bill Murray, Dan Aykroyd, Sigourney Weaver, Rick Moranis, and all the rest weird situations in which to play. Good actors given unusual things to do - what else does a movie need?
In recent times some have found a Reagan '80s pro-business, anti-government regulation subtext in the movie, with the small businessmen of the Ghostbusters contending with the petty bureaucrat played by William Atherton (the go-to slimeball character actor for about a decade). There's a little bit of validity to this argument, but I'd say that primarily the attitude of Ghostbusters is more in the classic American tradition of refusing to kowtow to authority of any kind, be it a government pencil-pusher or a forgotten deity. If the Marx Brothers had ever made a ghost movie, it would probably look something like this.
More than anything, though, this is the Bill Murray show, pretty much refusing to take any given scene seriously, nudging the audience, but never getting obnoxious about it, the way that Jim Carrey or Eddie Murphy can be prone to do. Indeed, there's a touch of pathos to Murray's performance, especially in his scenes with Sigourney Weaver, that would later blossom (if that's the right word) in Murray's movies like Groundhog Day and Rushmore.
(Presented as part of the Class of '84 Blog-a-thon hosted by This Distracted Globe.)