In Pictures: Apple’s most important iPhone upgrade...
The introduction of the Retina Display with the iPhone 4 is arguably a watershed moment in iPhone history. Packing an astonishing 326 pixels per inch, Apple's Retina Display brought a clarity and vibrancy to mobile displays that most people hadn't previously experienced. It's not hyperbolic to state that once you've used a mobile device with a Retina Display, it's impossible to go back. If you hold up any Retina Display iPhone next to an older-generation model, the difference is jarring. Steve Jobs once called the iPhone 4 an A+ upgrade, and the Retina Display is largely why.
In Pictures: Apple’s most important iPhone upgrades over the years