This is the rare case where a sequel is actually better than the original. Considering that original is the cheap and nasty Ghoulies, it's really not much of an accomplishment. Anyway the plot here is that the Ghoulies make their way to a carnival where business is poor. Their presence manages to help business pick up but of course they do what Ghoulies are meant to do and start killing people.
What makes this a better movie than the first? Well for starters the carnival setting is more interesting. The special effects for the Ghoulies is improved over the first. The cast is better, helped in large part by veteran Royal Dano and "little person" Phil Fondacaro. But ultimately it's the camp humor that this movie has that elevates it above the previous movie.
All this being said about how it's an improvement over the first Ghoulies, it's still not a very good movie. It's watchable enough for a movie of its kind. But let's not get carried away and say it's anything better than that. So, better than the first Ghoulies but still not very good.