I use a zero to five nods scale for ranking perfumes I review, and you will find these in the tags on each post. This is a very subject, internalized ranking system that I primarily use to keep track of (and curb my) impossible shopping w/r/t perfume. Because I can't even follow my own rules, I sometimes add a half nod when something is slightly better than a whole number but not quite good enough to meet the next level.
5 nods: Totally Genius. Possibly the "best of" a category I've tried (i.e. "best iris; best rose-chypre"). Buy immediately. Hang the cost -- you must own a bottle. If you find it cheap, you may even buy two.
4 nods: Really quite nice. Maybe not the best of, but high quality and worth owning. I'd go out of my way to buy a bottle.
3 nods: Good, but not great. I'd certainly take a bottle if one were offered me, and I might even buy one if I could find a good deal on it. Also, sometimes very good, but very good in a category of scents where I have found several 4s and 5s, which, by comparison, makes it a 3, not for any failing on the particular scent's part.
2 nods: Not terrible; decent and something I can understand some people liking and owning, but not something I'd buy on my own even at a huge discount.
1 nod: I really don't understand why anyone ever paid money to manufacture and market this. Might have been a great idea on paper, but completely falls apart in execution. Not worth it at any price point.
0 nods: OH DEAR GOD, why did anyone make this? Not only will I not wear this, I will actively avoid encountering it again. The rare and dreaded "scrubber."