The OpenMoko phone also had a higher number of pixels-per-inch than the iPhone 4. And this was years ago, by a no-name hardware company.
The reason other phones don't have a "retina display" is because it's expensive, and the other phones are trying to win market share by being cheap. Sadly, this works better than making a quality product.
Given the retinal indifference threshold of 287ppi@12inches, which was given in a recent HN-linked and praised article, 282ppi only needs to be a 1/4 inch further out for the pixels to fall into retinal indifference. Pretty nice for a 2008 phone.
The reason other phones don't have a "retina display" is because it's expensive, and the other phones are trying to win market share by being cheap. Sadly, this works better than making a quality product.