I understand what you are trying to say. BUT. The sentence I bolded isn't exactly true in this case. If your sentence was true, then there would be no need for app developers to add new graphics to their apps.
Sigh. No. App developers and web developers are not working with the same constraints. For starters, app developers
don't "need" to add new graphics. Using the same old artwork does not make anything worse. Everything looks effectively the same. All lines are exactly the same size, in exactly the same locations. The only visual difference is a result of the tighter pixel pitch, which
sharpens, not blurs, the edges of upscaled content on a retina display.
App developers generally chose to upgrade artwork because there are fixed parameters to work with, and they can greatly enhance the experience by perfectly tailoring everything to the display.
That isn't feasible on the web. You have no control over the pixel density of the displays your users use, the resolution, the color profiles, or anything else. Using the de facto web standard of 1280x1024 at 96ppi is the typical reference point. But common computers in use have displays ranging from 90 to 130 ppi, so you have to factor that in. If your site is fixed in pixels rather than a relative measure (e.g., ems), that means the physical size of your site is going to change from device to device. Any user of any browser on any display who changes the physical size is going to require resampling. This isn't new and has nothing to do with retina displays.
With the physical scale of the iPad running an effective 1024x768 at 132ppi in the browser for both retina and non-retina images, all elements are going to be displayed at the exact same physical size. Since there are no lines or pixels that need to be divided fractionally, the images will present in the exact same form and the same level of detail on both devices. You
can engineer elements to take advantage of the native resolution to allow deeper zooming of raster images, but you don't lose anything by skipping that work.
Mobile Safari allows for arbitrary scaling of web pages, which is where the issues start to appear, because the resampling has to make best approximations based on the zoom level chosen. This again has nothing to do with retina displays (the same process occurs on an iPad 2), and in fact is
improved on the iPad 3 because there are twice as many pixels in the same space, allowing for resampling to do even closer rounding with the math.
As you say, the images would just look normal. But they DON'T. The whole point of using quadruple the resolution of the original iPad wasn't so that the old apps would look just as sharp. It was so they could maintain the same aspect ratio making the old apps usable.
Again, you're almost there, but you're missing a key element. Maintaining a 3:2 aspect ratio was possible with any number of other resolutions already available on the market without massive R&D requirements (e.g., any of the several 720x480 displays out there). They spent a ton of money on the retina display specifically to maintain the same level of detail on the screens using the same apps, because perfect 2:1 scaling introduces
zero blurring, pixelation, or other distortions.
On the iphone 4, any graphic with an old pre-retina app, that wasn't being rendered in real time (ex. text, vector graphics), was blurry.
No, it is
not blurrier than it was on the 3GS or earlier, and "being rendered in real time" has nothing to do with it. The non-retina display is the blurrier image because of optical effects. The retina display with pixel-doubling will always be sharper, because the gaps between pixels are smaller.
P.S. Did you not see the post right below mine? You really think that person has been wasting their time? He even tested his websites in the emulator and had a clear grasp of what needed to be done.
"Waste" is a relative term, but most importantly, that website has virtually no raster artwork in its layout. What he did mainly was allow the photo galleries on the site to serve up higher-resolution images, a fine advantage on a photography site but not fundamentally different from just displaying the high-res image to start with and letting the browser rescale.
Those aren't the parameters of most web developers, and the marginal gains are generally not worth the extra work and data transfer volume.
I read a couple reviews today. Both mentioned the website issue.
If you read the quotes, they're talking about it standing out in contrast to other elements and not standing up to zooming, not on its own merits. That's reflective of the web reference standards being out of date. It doesn't really have anything to do with "retina" or not, and it's something people have been dealing with on all kinds of devices for several years. You can see the same thing by zooming in on your browser today, as many people do.
The only solutions are vector graphics, giant images, or tedious JavaScript and CSS detection hacks. None of this is caused by or unique to the iPad's display.