There are various rendering presets in emulators designed to simulate CRT effects (like scan lines and softness/blur filters), but it's not great really. Cathode ray tube televisions worked very differently to modern flat screens, for instance pixels aren't strictly defined, so they can render any resolution, up to their maximum supported resolution, without upscaling issues. This also means the pixel edges are less harsh, even at max resolution..A lot of the text in menus/subtitles, and textures in games, are designed to take advantage of this softer look, and when displayed on a modern flat screen, look really blurry and have poorly defined edges. Or they have weird aliasing that you'd never be able to see on a CRT due to the "softness" of the pixels. Shadows and blacks/greys suffer a ton here, even in high quality textures without compression artifacts.
The best way to get close to the original look on a flatscreen is to use an HD texture pack with a faithful/true to original design with an emulator, or create one yourself. So redoing all the textures and text for an HD flat screen, trying to recreate the original look as much as possible. But not everything can be re-created, like an effect in a menu that takes advantage of CRT scan lines is just going to look like a line traveling across the screen, not matter what is done to "upscale" it. There are some very good results out there for GameCube games in particular. Lots and lots of work though to make one yourself, I know because I'm trying to lol.
But even in that video where they get the smoke and cloud effects to look correct in the introduction, slippys picture, the text and the blue part of the aircraft look worse on the "LCD CRT", because of what I said earlier.
Has anyone tried making a screen overlay that simulates CRTs?
There are various rendering presets in emulators designed to simulate CRT effects (like scan lines and softness/blur filters), but it's not great really. Cathode ray tube televisions worked very differently to modern flat screens, for instance pixels aren't strictly defined, so they can render any resolution, up to their maximum supported resolution, without upscaling issues. This also means the pixel edges are less harsh, even at max resolution..A lot of the text in menus/subtitles, and textures in games, are designed to take advantage of this softer look, and when displayed on a modern flat screen, look really blurry and have poorly defined edges. Or they have weird aliasing that you'd never be able to see on a CRT due to the "softness" of the pixels. Shadows and blacks/greys suffer a ton here, even in high quality textures without compression artifacts.
The best way to get close to the original look on a flatscreen is to use an HD texture pack with a faithful/true to original design with an emulator, or create one yourself. So redoing all the textures and text for an HD flat screen, trying to recreate the original look as much as possible. But not everything can be re-created, like an effect in a menu that takes advantage of CRT scan lines is just going to look like a line traveling across the screen, not matter what is done to "upscale" it. There are some very good results out there for GameCube games in particular. Lots and lots of work though to make one yourself, I know because I'm trying to lol.
As for your original question, some people are trying to do just that
But even in that video where they get the smoke and cloud effects to look correct in the introduction, slippys picture, the text and the blue part of the aircraft look worse on the "LCD CRT", because of what I said earlier.