So how do you rate "so bad they're good" movies?

After watching Troll 2 and The Room, I'm struggling with this. I can't rate them 9-10 because that would put them alongside movies like Goodfellas and Pulp Fiction, etc. which would seem crazy to me. I can't rate them a 1-2 because they're not as godawful as some of those movies which are bad without any redeeming features. And if I rate them a 5/10, that would make it seem as if they come across as "meh" movies and these are anything but boring/average.

So I've sort of settled on a 1-5 scale within the 1-10 rating system with a 5 being the pinnacle of bad movies. But I don't know, I know some people rate movies based purely on entertainment value... it's still a puzzler, at least to me.