James-F wrote:

VGA or DVI can't do more than 1080p in 60Hz, not enough bandwidth.

Not true. My computer is pumping 2560x1440@72Hz over DVI as I type this.
My old 21" NEC CRT can also take 1920x1440 over VGA, well over 1080p. I usually run the thing at 1600x1200 at 85Hz. 😀

^I can confirm 1920x1440@60Hz through ordinary VGA cable. IIRC max through VGA is 2048x1536 @60Hz? Or even 75Hz. At least that's the highest I've seen for a CRT monitor,

archsan wrote:

I'm not even sure there's a 4:3 mode with my 4K monitor (likely not).

Let me amend that, the monitor does 4:3 automatically with the "Original" setting (one of the Ratio options -- the other two are "Wide" and "1:1")

Also there's an adjustable upscaling feature from LG called "SuperResolution" mode that when set properly could give quite a clean image, no matter what (lower) resolution is chosen. I prefer this look to a much blurrier one. This would be the feature that you retro gamers would want to look into.

P.S. Oh damn, I just realized that of course a forced 4:3 mode is still required for many things. 🙁

I mean games with native res of 320x200, 640x400 will usually look nice displayed in 16:10 ratio (not too wide/squeezed). But others will have their own preferences.