Everybody who's saying that the studio is responsible for watering down the sequel really, REALLY needs to read Aykroyd's original script for the first movie.
You got it anywhere handy?
If memory serves, wasn't it really over the top with the Ghostbusters going through time and space catching ghosts? And a ghost like Stay Puft, wasn't an "end boss" kind of ghost, but rather a regular one they would catch?
I don't think it wasn't until Ramis and Rietman came on board before that got scaled back to a more "realistic" setting.