I hope what I suggests helps, but it may not.
Fahrenheit is doggone unique. I don't think its greatness, weirdness, and amazing range is duplicated anywhere. I too have heard that Creed's Green Valley resembles it, but when I sniff Green Valley I don't get the great rush that Fahrenheit gives me. So I stick with Fahrenheit. I also smelled Creed's Chevrefeuille Original (a honeysuckle scent) hoping to get Fahrenheit's pleasure topped, but no go, it was a let down in comparison. Maybe you'll just have to stall a Dior customer.
Grey Flannel is a beauty I like too. Nothing out there is a clone of it, and it doesn't clone anything itself. It is, however, a scent with a lot of violet. Violet is that cold nose-stabbing clean spike that kicks out of Grey Flannel, so maybe you'll find something you like by searching for a violet scent. My favorite straight violet is by Molinard. "Les Fleurs de Provence" series, "Violette." It smells like French violet and vanilla candies that come in small metal tins. It might be close to feminine, but hell, it is great at what it does and I like the cold danger it stabs me with. It is no where near the range of Grey Flannel, but it is similar to that spike of GF.
What I suggest is that you stay with those two for what they are, but there are similar scents in style, not ingredients that might please you. These two are wet and mossy smelling to me (Fahrenheit is sometimes hot and burnt, thought). If you like that style you might seek out Celine Pour Homme, Halston 1-12, Kiton Men, and Nino Cerrutti Original. Green Valley fits into this slice of the fragrance pie too. There are others but I can't think of them now.
Good luck, but if you've got stuff you like in Fahrenheit, Grey Flannel, and Joop!, you've got rich and pleasing stuff already. There's always spin off options like Fahrenheit Summer and Eau de Grey Flannel, but...