I post these on /vr/ a lot but I think these webms perfectly highlight why the HD releases somehow don't look at good as the PS2 versions.

Don't own a 4K, I have a 5X (it's less expensive and an older model). It was worth every dollar I spent on it.

This webm was recorded off a 5X playing on original PS2 hardware.

>>11944614
PS2 games are with the Retrotink truly shines and IMO it looks better than the constant flickering on a real CRT.

Here's direct capture of MGS2.

This webm is made from Retrotink 5X footage.

If you have a CRT as your main TV for retro gaming, you can stick with that. For non-CRTs, I really don't know a better option for upscaling for everything without (perceptible) input lag if you value the accuracy of playing on real hardware.
If you are an emuchad, then obviously none of this applies.

The biggest argument I don't see much online is what is best for deinterlacing PS2: motion adaptive or blend.