As a rule, one should only use the gentle power of tenderness. It is best to peer deeply into the soul of your monitor (fluttering of pixels may indicate a positive response to your loving gaze). Its currently-displayed media should be closely-examined for an imbalance of proportions. Then, the ultimate question must be posed:
"Do you seek for your projected content to be extended beyond the specified standard?"

If the answer is a categorical "no", one must respect that its wish is not to be overridden, and simply remain satisfied with the present stage of your blossoming relationship. For now, 4:3 imagery can be quite gratifying, and later, there will always be time for the alluring 16:9 material.

I don't like a distorted ratio either. I use the original one as much as possible

That depends completely on the type of game. For point&click adventures bigger isn't better once you have to move your head.

For racing games on the other hand a lot of stuff is happening in the peripheral vision. And it is completely natural to move your head to check mirrors, observe cars alongside you, focus a corner apex and so on and so forth. Here screen size massively improves immersion especially if you don't have the space or money for a big multi monitor setup.

Always 4:3/Original proportions here.

If the game has Widescreen but it plays well in 4:3, I mostly try to play it at 4:3, and when it plays weird or it was not programmed to play in 4:3, I tend to switch it to 16:10 or 16:9.
Even though my monitor supports up to 720p (its small, on purpose.) I tend to play games on smaller resolutions on their original proportions.

I use Widescreen if the game supports it.

I use widescreen if there are tweaks / mods that enable it.

I will tolerate stretched UI. I will not tolerate stretched game.

So if wide screen is possible, but it stretches a circle map into an elliptical map, that's fine for me. If all the characters become thick when vertical and long when horizontal, then I will stick with 4:3.

Eg:
I would play GTA or Mafia in Widescreen.
I would not play Syberia 1/2 in Widescreen.

Many older games were made for 4:3 aspect ratio, but with engine remakes (OpenXcom, CorsixTH, fheroes2, JA2 Stracciatella, etc.) they can be played on widescreen :)

Widescreen takes different resolutions than square.
Just playing Far Cry on 1366*768 instead of 1024*768 stretched (forced) to a wide screen by the driver.
I always change the resolution to fit the monitor, some games like Baldur's Gate 2 Complete need the desktop to be clocked on 800*600 to display a nice full screen without borders...

Practicing with:
10.1" - WSVGA @ 1024*600 (800*600 looks good)
24"wide 16:9 @ 1920*1080FullHD (1360*768&1600*900 looks good)
55"wide 16:9 @ 3840 x 2160UltraHD (1366*768& 1600*900& 1920*1080)

Apart from 1024*768 and 800*600; all other resolutions are either stretched too much or squeezed on full screen,
the bigger disproportion in ratio the bigger the "black bars" are.

You are looking for "just right" resolutions for your screen to keep the game spread through the entire screen without changing the aspect ratio. 1024*768 isn't for wide screens so as many other resolutions.
1366*768 is the best overall solution for wide screens as good as 1280*720...
or
1600*900 exactly 16:9 and 1920*1080FullHD in good shape
or
Push it to the limits with 3840*2160UltraHD

While it's not easy to change the resolution of the videos,
most video games make it easy. (No more side darkness)

good luck 🤞

Edit: Games with only ->1024*768 and 800*600<- or 1280*960 or 640*480; 4:3; can be stretched 16:9 and I always do that : ) or play in a window. The solution above seems sensible : ) I remember using a blanket to cover the sides of the screen, or cartoon cutouts to hide window frames lol since emulators and stuff it's all achievable..... The simplest and most effective way to play on 4:3 full screen would be to get an old monitor from 00-09' or to befriend those sidebars : )

I don't mind black bars on any side of the screen, assuming that it is caused by integer scaling, but I also don't totally refuse to utilize any means to use bigger and wider resolutions as long as the original pixel aspect ration can be maintained and the added visible distance doesn't cause any issues like enemies popping in out of nowhere or if the game now allows me to snipe them them outside of their aggro ranges.

Unfortunately widescreen computer monitor makers don't seem to understand that 320x200 is not actually a widescreen resolution, meaning that even if there are aspect ratio correction support in their menus, they don't let the users to set the aspect ratio for that resolution and even if one would plug an OSSC-box between the monitor and the old gaming computer's VGA port to force a bigger resolution, should a game use different resolutions and/or frequencies like Descent with its first person view and 3D map view, it may be better to just use a TV with your old computers as TVs may still actually remain in 4:3 mode until told otherwise rather than reset the aspect ratio setting over any excuse and they are also far more likely to have a quicker way to switch the ratio than computer monitors which tend to hide that far too deep in their menu trees.

I try to use the original aspect ratio whenever that's possible, and try to make a judgement call if the game offers both, based on when it came out. Then again, I am one of those who also likes CRT filters, I try to get games to look "more or less" as I would have experienced them at the time.

No. I use the biggest size available to my monitor, never stretching the game out of its own 1:1 ratio. When there is relevant unused space left, I play the game windowed as the space comes handy to switch to guides, maps, or to my own notes. Sometimes the performance says no, or alternating windows cause troubles with the sound and volume, then I let the black bars take their place.

I think that resolutions below 640x480 (or possibly 640x400) haven't been supported for many, many years, I seem to remember that even my monitor, bought in 2007, behaved oddly with them if running natively (but haven't done that in a long time). Or it may be an OS thing and support was dropped at least since Vista, if not XP. Or maybe both.

If only, as then surely my old DOS computers wouldn't have this problem with my 1920x1200 LCD displays.

On my PC I handle it the same way as on my TV. I'd rather have black bars than any stretching.

I'll take black bars on the screen over a distorted image everyday and twice on Sundays I'm the exact opposite. If the image is distorted with no way to remedy it, I'll never use that particular piece of media,