Oooooh you have no idea! I can name quite a few things worse than that, like pink or violet bars!

Always keep aspect ratio for me. I'd rather have black bars, which can be quite awkward on an ultrawide monitor, than have a stretched image.

Aspect ratio. Always. Distorted image is one thing I really can't bear having, be it video, games or photos. I know some people don't mind, for me it's unfeasible if a circle is not a circle.

Keep aspect ratio, no matter what.

In fact, I've been known to not bother with otherwise interesting sounding youtube videos of games because of the aspect ratio issue.

Ugly stretch marks or slim and fit?
Decisions, decisions...

Anyone who doesn't use keep aspect ratio baffles me. Same for movies. Even if you think the "black bars" are super annoying, how can they possibly be more annoying than distorting the whole picture? Baffling.

I do miss my 16:10 monitor though, which I thought was perfect for PC uses.

Aspect ratio. It can be really distracting otherwise..

aspect, I noticed this too, but I just edit the conf file.

I prefer to keep to original aspect as much as possible. Same with films.

Rare exception to be made in certain games, mostly ones where the aspect ratio doesn't impact the point of playing the game.

Correct aspect ratio always. I will put hours of work into getting things in the correct aspect ratio if necessary because I find a stretched image incredibly distracting. I keep telling people this (but maybe I've not told you this before), but that's not what that option is for. It's for correcting VGA resolutions that used non-square pixels and it's very useful, but it won't help if the config has been set up to stretch things to full screen.
What do you do when watching movies on a 16:9 screen? Most films are shot in an aspect ratio wider than 16:9 and will (should) be letterboxed on a normal TV.

Always keep aspect ratio.

If not for that one answer, I'd wonder why's this even a question. Keep aspect ratio, of course! (Granted, for me that's not much of an issue for older games as I have a 1280x1024 monitor. But would still try to make it effectively 1280x960 for correct 4:3 if that's what the original resolution was. The black bars are horizontal in my case, for widescreen images.)
I mean, black bars are like that part of your screen doesn't exist, so why would it bother you? It's just... not there, inactive, act as if the screen just covers the active part. But if the image is stretched, how can you act that it's not?

It's just that there are two different aspect ratio issues when it comes to DOS games. The first one applies to all 4:3 games and is fixed by telling your graphics card and/or monitor to maintain the aspect ratio of the resolution. The second one is specific to old DOS games and is due to the fact that one of the most common VGA modes was 320x200, which if you do the maths isn't 4:3 (it's actually 16:10). These games were generally designed for a 4:3 monitor so they were actually meant to be stretched to full screen on an old CRT, which gives you tall rectangular pixels. The aspect ratio flag in DOSbox is for deliberately stretching those games into a 4:3 resolution which your monitor and/or graphics card can then maintain the aspect ratio of.

Keep aspect ratio ^_^