Troll 2 has a reputation for being one of the worst films ever made in the horror genre, so I pressed "play" with modest expectations. There are indeed many plot inconsistencies, it isn't even momentarily scary, and "shoddy" does even not begin to describe the effects and production values.
But for all this it is an entertaining and original story. I can't think of many other films where the main characters face strict vegetarians as their adversaries. This turns out to be one of the monsters' key vulnerabilities as they loathe even contact with blood and will engage in hand-to-hand combat only as a last resort. Joshua's deceased grandpa appears to him now and again to advise him on how to protect his family from the creatures (they're called Goblins in the film, not trolls). He even has some miraculous powers which he occasionally uses against the chlorophyll-consuming villains but Joshua has to make some drastic decisions on his own when his unsuspecting parents are about to be poisoned.
And it really does deliver laughs - yes, sometimes in a "so good that it's bad" sort of way, but quite often it's meant to be funny and genuinely is.
Judging it for what it is - a camp low-budget comedy horror - it would be worth a 7 on a 1 to 10 scale, but I'm rounding the score down on account of the disgracefully lazy special effects. I can tolerate the fact that the goblin costumes look as if they're made of starched brown canvas, but in the scenes where people are "vegetablised" after eating the tainted food, it seems the best contrivance they could come up with was alabaster shop mannequin slathered in green hair gel! Effects like this don't even deserve the name "special"!
I'm also a little puzzled by the 18 certificate - there's really nothing in this I wouldn't let the average 12 year old watch.