The tricky thing with Ghostbusters is that the original was a lot darker and more serious than people tend to remember. It was a product of the early 80s, in which many films, like Gremlins, Poltergeist and Indiana Jones and the Temple of Doom, were rated PG and targeted at all age groups, but were relatively scary and sinister. We sometimes think of Ghostbusters as a lighthearted comedy, but it really wasn't at all. It's likely that no sequel will ever really compare to it because a film like that won't be made again. Even by the end of the decade, Hollywood had already changed and "lightened up," which is why Ghostbusters II and Indiana Jones and the Last Crusade (both 1989 releases) were lighter in mood than their predecessors.
Since Ghostbusters will never be duplicated, it's tricky to make a sequel because it's going to feel different and, thus, disappointing. One of Ghostbusters II's problems is that it felt different than the original. The Real Ghostbusters cartoon, as fun as it was, also felt different because it was very lighthearted. The 2016 "remake" had the same problem. The best that you can do is identify as many original elements that worked, that fans remember fondly and that will still play nowadays and hope that fans are OK with the necessary differences. So far, nothing has exactly pulled that off, which is why it's a franchise that has always struggled to live up to itself.
