I rate products on a scale of 0 to 5 based on how much I like them.  The scale is as follows:

0 = Terrible useless garbage (product actively did harm to my skin)

1 = Poor performance (product made my skin react negatively)

2 = Neutral performance (product did nothing for my skin)

3 = Good performance (product was mildly beneficial for my skin)

4 = Great performance (product was beneficial for my skin)

5 = Excellent performance (product actively improved my skin)

Sometimes, when I like a product so much I will give it holy grail status.  When that happens, I give the product the Seal of Approval!