Kent Akgungor df">compares the 2014 Retina 5K iMac to the 1984 original Macintosh:
When first released in 1984, the Apple Macintosh shipped with a black-and-white 512 x 342 display. Fast forward 30 years to the release of the iMac with Retina 5K display, which ships with a 5,120 x 2,880 display with support for millions of colours. That’s an increase from 175,000 pixels to more than 14.7 million – an 8,400% increase. 80 of the original Macintosh displays fit within a single Retina 5K display1. I'll repeat the last sentence: 80 of the original Macintosh displays fit within a single Retina 5K display. I got a chance to play with a Retina iMac at the Apple Store today --- it really is a terrific screen. The only problem with it, for me, is the screen, at 27 inches, is so massive that it feels a bit overwhelming to me. For my taste, I'd prefer a smaller, 21.5" version, which has yet to exist.