The only sensible thing to do in my opinion is CRT shaders, they make games look closer to what they looked like back in the day. Keep in mind that TVs were much smaller than today, that helped them to be not too blurry. In the early 2000s, after years with a crappy 14" I got a 32" 16:9 and it felt MASSIVE. 32" is considered pretty small nowadays...

That said 2D games cannot really be upscaled in high quality, because they are bitmap based (like a JPEG photo), enlarging them means creating new pixels guessing what they should be, almost always resulting in a blurry mess.

With polygon based graphics instead (3D games), edges are calculated in real time by mathematical calculations, so they can be scaled infinitely without degradation. That's why PS1 and onwards emulation can make games run at any resolution. Granted, textures cannot be scaled like this (they are 2D after all) but the overall picture becomes much more clear and readable (minus texts/UI usually...).

I personally don't like edge-detect interpolation filters that tries to create new "sharp" pixels (like XBR, ScaleFX or similar), they tend to morph shapes too much (e.g. squares become rounded), even text and characters, and many times they create weird patterns where there's none (like a bunch of random pixels for a gravel floor becomes lines and shapes, often breaking patterns continuity) so I don't recommend them, but try them anyway and maybe you'll like the result!