I think the DFRPG game would lend itself to the Supernatural (TV Series) setting or a setting like that of the Eden Studios games (WitchCraft, Armageddon). That said, there are the other RPG games for those settings and it'd depend on how wedded you and your group is to FATE. The Hellboy and John Constantine comic book settings would probably work as well.
This. I've actually designed some Constantine/Hellblazer-like characters and scenarios last summer, and it seemed to fit rather well. Also, I think it would work better than the Unisystem for settings like WitchCraft and Armageddon, but I could be wrong (and a bit biased, since I like my open-ended magic).
I actually just started using the mechanics of The Dresden Files to power my game of Victoriana. Victoriana is a game now owned by Cubicle 7 Studios and is powered by the Heresy Gaming Engine. It is set in an alternate version of London in 1867. It carries some of the popular aspects of steampunk (airships, clockwork limbs, etc) with a heavy dose of fantasy (magic, fantasy races, etc). The core mechanics seemed clunky, and became rather bothersome, clunky and limiting for my players and I, especially when it came to the magical side of things.
Instead, we began implementing the mechanics for magic from The Dresden Files, and my party has not only changed gears, but they are wondering what they
can't do with magic while loving the Aspect and Manuever systems.
Currently, I have five players at the table, four of which are spellcasters (Kinetomancer, Ectomancer, Thaumaturgist with Pyromancy, and a Thaumaturgist with Spirit magic very much like Molly's). During the first game session, the Thaumaturgists were having a party determining the different things they could do to their target, the Ectomancer felt more comfortable with her chances of success, and the Kinetomancer loved the idea of the descriptive magic that doesn't cost stress. I think it's a success so far.
The only major changes I really implemented were removing the Resource skill and replacing it with a small Refresh Cost based on social standing (as the original mechanic required you to purchase your income) and removing the major parts of the Lawbreaker Stunt (as the "Laws of Magic" from the setting are MUCH different). The other thing I did was allow certain "creature features" to be purchased by "Pure Mortals" that are of different races (such as a Wolf-Beastman having Echoes of the Beast).
Otherwise, the game is running as-is, and it has met with success for game one, and everyone is looking forward to game two. My final player (missing due to finishing teaching elsewhere, will be joining in a few weeks once we find a place) also enjoyed the DFRPG approach to character creation over the original Victoriana mechanic.
If you ask later, I'll let you know how the next game goes. Game two with the new rules is next Friday. ^_^
--Crion