I'm not sure how you could be getting slender characters with 4:3. Most older games would have a 4:3 aspect ratio so if you were distorting the aspect to fill a 16:9 or similar widescreen form factor then the objects should make things look wider not thinner. Thinner would only present if you were taking a widescreen image like 16:9 and trying to cram it into a 4:3 space. Which might happen if your monitor is a 4:3 shape and you were setting it to use a 16:9 resolution (which some will allow you to do)
Distortion only happens when a bad ratio is in the mix, and is suggestive that something is wrong. By default your monitor should be set to a resolution with the same aspect ratio as your monitor's shape. Then when possible stick with that resolution for everything. On older games that use old 4:3 screen resolutions your options may vary depending on the application, and monitor settings, but 4:3 resolutions belong on 4:3 monitors, and 16:9 resolutions belong on 16:9 monitors, etc. My guess is your monitor is 4:3 and that is why 4:3 resolutions look correct, because they are.
When it comes to personal taste I am a big fan of the modern 16:9/16:10 form factors over the older 4:3. It feels like a much more natural arrangement. And when gaming it's useful to have good visual room on the horizontal axis. I wouldn't step back to 4:3 if you paid me.
SirPrimalform: I'm very fussy about aspect ratio distortion (I can't watch a film at someone else's house with it stretched, drives me mad).
Agreed. Though it was part of my job to know when aspects were out of whack for a good while there, so I may be a bit stricter than the norm.