Yeah, I agree with
@SLiV3R. On a high-res platform like phones/desktop monitors/TVs/etc. you can do some pretty attractive-looking scaling while maintaining most of the sharpness in the picture. But on the tiny 3DS screen, the sharp 1:1 pixels are probably nicer than the benefit you'd get from accurately rendering the original platform's aspect ratio. e.g. Neo Geo games are technically a
tiny bit wider than 1:1 pixels. You could accurately represent this on 3DS, but you might as well have great-looking 1:1 pixels instead of fussing with getting the aspect ratio right. Now, the further a platform deviates from 1:1 pixels, the more odd it's going to look if you keep using them, but the line where it becomes too far will vary from person to person.
For me, the only platforms in RetroArch 3DS currently that really push it are the CPS-1/CPS-2. I know the Earth is technically 27 miles wider than it is tall due to the planet's rotation, but the CPS platforms take it way too far.
(Second shot is how it is intended to look, at ~294 pixels wide.)
