Great fragrances, for me:
___Structure & Dynamics___
-- At first, they smell like a nearly harmonious musical chord and NOT of one particular note. Then, upon further "listening" I might be able to pick out a note or two -- an INSTRUMENT or two.
-- Some, very well designed fragrances, have notes which stand slightly above the chord. These are exciting and fun to "listen" to as I never know where they'll go and they maintain interest. These "jagged" notes are not required for a great fragrance, but wonderful when they are included.
-- A great fragrance will be structured for its purpose even if that is unto itself. Office, romantic, anytime, male, female, unisex, etc.; it will fulfill its role. A scent liked anytime will probably not be loved at any particular time. This is the fragrance equivalent of "he who tries to please all, pleases none". This is only a generality; there are always exceptions.
-- The dry down. Linear (staying the same) or leaving the base notes. Either way, they should last 8 hours. A great fragrance will maintain its composition or dry down into something pleasant.
This is personal preference. I like leather, vanilla, pipe tobacco, cinnamon, ambergris, woods, CURRENCY, the sea, cut lawn grass, etc. Really, this list can get lengthy. I even like bizarre things like a little chlorine.
The ratio of oils to alcohol is important. Obviously, higher oil/absolute content usually leads to better longevity - but not necessarily. Too much oil/absolute and there may be projection issues. The notes themselves must smell like their natural or unnatural counterparts. If it isn't found in the real world, then I guess it must simply be appealing. Whether this is achieved through more or less processed means, I really don't care.