I think this is an interesting topic. I find certain common themes in some of the houses, or subsets of the scents. Some of these are discussed in places, but never compiled. I'd be interested in seeing this extended.
For example, there is a sort of continuity of a specific woody note among all the Gucci PH, PH II, By (EDP), By (EDT), and By PH (EDT) scents, with a pseudo-chypre thing distinguishing the By scents. I think that a large number of Creeds have certain similarities, but I'm a bit weak on the exact nature of them.