I agree with what @epeli said, except instead of setting the game to 2x scaler, set it to 960x540. That will keep the font from looking fucked up because its a perfect 1:4 pixel mapping onto 1920x1080. You won't split the rendering of the low resolution font and graphics onto anisotropic subpixels, which is what makes low resolution games scaled to high look both blurry and sharp at the same time.
To be clear, in draw.ini set graphics mode to 4 or 5 (5 and playing with
borderless gaming is superior for multi monitor users IMO, mouse is still trapped in window until you alt-tab), the resolution to your desktop's native 1920x1080, and GPUBlt=1. That's it for ddraw.
In f2_res.ini, set graphics_mode=0 which passes along game window resolution control to ddraw. Put scale_2x=0, and set the screen resolution to 960 and 540 (600 for
16:10 owners). For fullscreen colors, set it to 8, and all the other graphics options are the same. Windowed does
not need to be set to 1 in the subsequent options if you're using dx9 windowed mode, ddraw will handle that.
edit: for reference, this is how those settings make the game look:
pictures
edit2: This works exactly the same way for Fallout 2, FYI. For Fallout 1, you have to use a much older version of sfall, Crafty's 1.7.6 and I don't believe rendering in a window works - you have to run it fullscreen 960x540/600. That means adding the resolution to your display driver. This is easy on nvidia, harder on amd, either way: google it.