Films like Ghostbusters are inseparable from the '80s -- self-mocking and smart, yet lowbrow and mainstream, they rescued us from the unfunny film comedies of previous times. (If Ghostbusters had been made earlier, it would have been much less funny. If it were remade today, it would probably be much dumber, like TV's Buffy the Vampire Slayer.)
Like Bill Murray's other top comedies, the slightly more subversive Caddyshack and Stripes, Ghostbusters passes the most important test of cinematic greatness -- no matter how many times you've seen it, you may end up watching it again when it comes around on TV. Murray, Aykroyd, and Ramis are postgraduates in "parapsychology" who pretend to investigate paranormal phenomena (the movie begins with Murray trying to pick up a coed by convincing her she's psychic) until they're kicked off campus. So they start a business and become celebrities when they start capturing real ghosts. This cheesy premise is handled so smoothly that there is never a confusing moment, something screenwriter Ramis would achieve again with Groundhog Day, an equally odd concept which also worked. Unlike Groundhog, Ghostbusters is strictly for laughs -- which doesn't mean that it's dumb.
Ghostbusters is Bill Murray's movie all the way -- Ramis and Aykroyd wrote it and costar, but they mostly serve as straight men for Murray's irony-soaked one-liners. Everything about the movie is goofy but somehow irresistible, from the Ray Parker Jr. theme song to the climactic marshmallow man. The supporting characters are likewise wacky but logical, including Potts as the jaded receptionist who puts the moves on Ramis ("Do you have any hobbies?" "I collect spores, molds, and fungus.") and Moranis' nerdy tax consultant who ends up possessed by a Mesopotamian demigod.
The script is not flawless -- in an unnecessary subplot that stalls the movie in the middle, the boys get busted by the EPA. (Only in the '80s could everything, even ghosts, be blamed on too much government.) Otherwise, the movie is fun from start to finish, when the 'busters destroy the evil Sumerian demigod atop a Central Park high-rise and Ernie Hudson (as the token African-American ghostbuster) jumps in the air and yells "I love this town!" -- reducing the whole movie to a New York City joke.
One of the most popular comedies ever, Ghostbusters inspired many subsequent blockbusters (most obviously Men in Black, which even threw in a couple of NYC jokes itself) plus a children's cartoon. The entire cast reunited for an uninspired, but not bad, sequel in 1989.
Now available on a two-DVD set with the sequel, you get not only a collectible booklet of drawings and errata, but also a commentary, deleted scenes, and various featurettes.
Aka Ghost Busters.