Just do what you want, it's a video game. Pick whatever is subjectively most visually appealing to you. Modern games have lots of visual settings too, partially for that reason. For the most part these don't affect gameplay.
As for what I think looks subjectively better:>>4k upscaling
Usually works for 6th and 7th gen games. 5th gen games just have too little detail and it ends up looking like papercraft instead.
Supersampling or something like MSAA looks gorgeous for these games though. You can smooth over the jagged edges without introducing a conspicuous juxtaposition of detail levels in all the flat polys and low res textures. >>texture filtering
Usually textures are designed with a certain kind of filtering in mind, so I tend to keep this the same.>>widescreen hack
Out of all of these it's probably the one that affects the gameplay the most since it alters the FoV. Some games are made much easier because of this. You're not really playing the same game, but I think the results from a purely visual standpoint are fine.>>overclock for 60fps
Fine with me. There's no justification for having poor performance when the option of having good performance is right there.>>PGXP
Eh, this could go either way. Most of the time swimming textures simply look bad - on a handful of occasions such as this pic, I think it gives them a little more depth. Most of the time vertex jittering is conspicuous, but occasionally it makes models seem animated. MGS is a good example. It simply depends on the game.
I really hate depth errors but PGXP can't fix those. It'd be nice to have fixed Z sorting in older games, incorrect Z sorting is an obvious visual defect that doesn't add anything to image quality IMO.>>Shaders
Not the worst thing. Scanlines and screen door effect did a lot to reduce the blocky look of low resolution video. You're probably better off just buying a CRT though.