The "Retina" display is not new! This is typical of Apple, release some old technology and put a nice, catchy name on it!
If you want a "Retina" display on any product, get a high resolution monitor. That's all a "Retina" display is. The native resolution is so high you can't see the PPI (pixels per square inch), just like magazines use DPI (dots per square inch).
There is a lot of math that goes into this, but to do away with all of that, see my source below. The new 27" iMac display is 109 PPI, where the new iPhone 4 and iPod Touch 4th Generation is 326 PPI. As you can see, this is not even half the resolution.
Just remember, the higher the resolution, and the bigger the screen, the smaller things appear! Would you <I>want</I> a "Retina" display on your computer? I kind of doubt it. There are already rumors that some people have a hard time reading the small print on the iPhone screen without zooming in like they had to do with the old iPhone displays (163 PPI), which is still a higher PPI than the iMacs.
The deal is, you don't get close enough to an iMac to see the PPI, like you do a phone. It would cost far more to make a screen that large with that high of PPI. Plus, sitting at a normal distance from the monitor, it would be almost impossible to read things!
It might be a nice concept, and thought, but it's not actually something you'd want, nor is it practical.
You can see on the list, the only other things close to the iPhone 4 PPI are the Toshiba Portege G900 and the HTC Touch Diamond 2. I'm sure an Android phone will be along soon to smash Apple's record, but for now, it is the king of displays.
Sources of help: