Those charts are based on pixel size compared to the resolving ability of the human eye (one arc minute for someone with 20/20 vision). I'm not sure that's necessarily a foolproof way to determine the perceptibility of increased resolution. For one, many people have better than 20/20 vision. But more importantly, humans can still detect differences well beyond that, even though they can't necessarily accurately resolve the detail. The ability to see misalignments in lines and shapes (known as vernier acuity) extends well below the level of resolving detail, to something like 1/8th of an arc minute for the average person. So while you wouldn't be able to see the actual pixels, you might be able to perceive minor jaggedness in lines from a lower resolution display that you wouldn't with a higher resolution.
Personally, I'm extremely skeptical of people's subjective impressions given how strong the placebo effect is. You see this all the time with audio. People will insist that their equipment or the resolution of their digital audio files affect the sound, but when they go through blind tests it's proven that they do no better than guessing in identifying which example uses the "superior" equipment or format. So someone comparing their new TV to their old one, or switching the resolution of the source and comparing isn't really conclusive at all.
However, I did read about one blind test that seemed pretty compelling. In it, they set up two 55" displays from Samsung, one that was 1080p and one that was 4K but both were the same type of display and from the same line. They calibrated them to remove as much of the non-resolution differences between them as possible (though they admit very minor differences in black levels and gamma response remained), built identical cabinets to house them in, and roped off an area 9 feet away for people to view them from. In the end, 97% of viewers were able to correctly identify the 4K screen. Though the testers readily admitted that the differences were pretty slight.
|