Is the iPhone 4, 4S, 5 truly retina display? Or have we been fooled to believing it is?

The screen is amazing. With no doubt but I have moments when I browse the web and I zoom into an image and its pixilated. I get confused why the text is so clear but the images are so pixelated on my iPhone 5 especially when I'm browsing the web.

I read this article and its pretty interesting

http://m.cultofmac.com/cultofmac/#!/entry/why-retina-isnt-enough-feature,50b81115d7fc7b5670801b63

let me know what u guys think