Retina for games may not be a big deal, but Retina for text definitely is: I notice the difference when reading on my iPad 2 vs my iPhone 4S. The distinction doesn't seem like much when you're in the middle of reading, but your eyes will definitely notice when you go from a screen that's Retina to one that isn't.
Well, the iPad Mini has a pixel density somewhere in the middle: it's higher than an iPad 1 or 2, but lower than a Retina iPad or iPhone (in fact, it's density is exactly equal to the pre-Retina iPhones)
The overall size of the screens affects your perception, too, I think: a large iPad screen feels different than a pocket-size phone screen.
