Do Apple's "Retina" really show the most pixels you can physically see?

[FunGui]

I have been arguing with my friend recently, he says that apple's retina display screen has the most pixels that you can possibly see and that buying any screen that has a higher PPI is a waste of money (the nexus 5, for example).
He says that watching a 1080p video on a nexus 5 would be pointless as you can't see the difference.
Can somebody enlighten me on whether any of this is true? I was sure retina display was just a marketing scheme by apple, spending less on sub-HD screens and marketing them as "the highest pixel density that the eye could see".
Can you tell the difference between 226 PPI and 445?

 

[clutchc]

On that small of a screen even that number of pixels is impossible to see w/o magnification. Put that many on a 60 inch display and suddenly you can see individual pixels. It's all a matter of perspective.

 

[velo3100]

Depends on the size of the screen. On a small screen 4.5 inches or smaller probably not unless you have a really good eyesight. On larger screens you will start to notice the pixels which is why bigger phones have a higher res screens. If you can see the difference between the new iphone and a similar size phone I can't say as I have not seen it in person.