First and foremost is that the GB2 actually continues the story from the first film and shows time has passed. The fact that first thing we see when the film starts is 'Five Years Later'... and then Dana with her baby on a chilly November/December evening says a lot when you think about. Not to mention it does give a strong follow up to things that happened in the fist film that most people gloss over. Let's remember, government agencies in their first film started to raise questions about the Ghostbusters, obviously first and foremost was the EPA... and there is a line in GB2 from Winston to Ray stating 'You conjured up a 100-foot Mashmellow Man'... meaning that the Ghostbusters were probably interviewed about what happened on top of central park west, leading to wonder if Ray's unintentional 'pop in there' moment was what caused the city, county and state of New York to shut the Ghostbusters down. Second, it actually gives everyone something to do, meaning Winston has moments to shine... even though his absence and lack of involvement with anything to do with the initial investigation into the circumstances of Dana's baby is something that still bothers me to this day.Speaking of said investigation, the whole situation involving little Oscar is never an afterthought, it is the center focus of the film with the pieces gradually falling into place for our heroes.
On the negative side is the amount of cut content from the film, some of which we see the montage that takes place after the court room scene, such as Louis and Slimer's interactions, which included Louis learning how to use a proton pack, as well as Ray being possessed by Vigo while driving the Ecto-1A after starring into the eyes of the Vigo painting at the art museum. As I mentioned before some elements from the first film are basically re-told, primarily Venkman and Dana's relationship, but one could argue that Venkman needed to mature quite a bit from where he was as a character in the first movie. The Ghostbusters not being in business at the start of the film could be counted as a negative, or at least the reason for it because by 1989, in the Real Ghostbusters cartoon, they established that there was periods of time when ghost activity would be pretty low for one reason or another, and that could've and should've been the reason why they had some odd jobs here and there.
One more thing of note, when Dana goes to Egon to get help following the opening of the movie, Egon's experiment regarding human emotions (the arguing couple and the child given the puppy) basically lays out the entire premise of the film regarding positive and negative vibes. I wonder how many people actually realize that.
