Or, how I determine it's a perfume I'd like to own a bottle/decant of.
I realize some of my criterions might not be objective but then again loving perfumes cannot be termed as objective as love is in there. :)
1. On the first inhale it makes me smile or relieves stress from my shoulders (Scarlett and Timbuktu respectively).
2. Notes are so well blended, you can't take them apart and they tell a story (Antonia).
3. It smells like the epitome of its category (Shalimar and Ambre Sultan).
4. It smells strange and compelling (Jardin du Nil).
5. It smells strange and interesting but might not be compelling to me (Vero Rubj).
6. It is so new to my nose that I can't resist trying to figure it out.
7. I lack words to describe what I'm smelling (as I'm overwhelmed usually - Antonia and Ambre Sultan again).
8. I simply love what I'm smelling as it hits all the right buttons for me, even though it might not get much love from everyone else.
P.S. I do plan on adding to this list as I realize I might be applying some other criteria I'm yet unaware of.