The way PD went about making fantasy tracks for GT Sport really upped the game in terms of realism. Previous games had fantasy tracks that were basically tunnels of trackside scenery like Trial Mountain and Deep Forest. Newer tracks like Dragon Trail use location data and build the circuit around that instead. You could actually go to the spot in Croatia where Dragon Trail would be, there's no track there, but still. It really gives those fictional tracks a good sense of realism and place compared to earlier ones and other courses from competing franchises, like the FIA commissioned a bunch of pop-up tracks for the Gran Turismo Championships. I'd have to say that GT Sport has the best tracks for converting into real life.
Now, if I had to choose, I'd probably go with Maggiore as my top pick, followed by Dragon Trail second and Sainte-Croix third.
Also something I don't understand is suggestions for public road grand prix courses like they had in the 50s and 60s. If there's a good chance of somebody wrapping around a tree and dying during a race, they should not be pursued. those kinds of courses should be left in the anals of history and sim racing.