My rating system:
5 stars - I am in LOVE, will buy in quantity and wear with abandon
4 stars - I like this a lot. Will probably purchase.
3 stars - Nice, but I'm not moved. I'd wear it if it was a gift, but not otherwise.
2 stars - Meh. Doesn't work for me.
1 star - Ew. Get this away from me - it's AWFUL!
Longevity ratings are simpler: 1 star for every 2 hours the fragrance lasts on my skin.
My standby? Beautiful by Estee Lauder. I've been wearing it since I was 15 and I love it still.