Everything that made the original so much fun seems to absent here. This is simply a "run of the mill demons on the loose wrecking havoc" slasher, but without the passion that graced the original.
There's nothing new in the story, in fact it seems like they ignore the first one altogether. Here, the demons run loose in a high security apartment building and, naturally, kill most of the residents in grisly fashion. The makeup effects actually seem less convincing here than the first time around. Although the actors weren't exactly brilliant in Demons, in Demons 2 they're actually a lot worse. You don't care about these characters, AT ALL. The plot is nonexistent, the music poor (apart from one Simon Boswell song), it's not scary in the least; it's just not that good.
Easily the worst film Dario Argento has been involved with and Lamberto Bava's also (Bava has a cameo in this film, not a very funny one).
Maybe 3 is too high a rating, but at least I could watch it all and didn't think of stopping midway. My advice; Stick to the original.