First, apologies if this has been already covered, but I have been searching in cocos2d, google, ... and found no response (maybe there is not response!)
When I first heard about the iPhone4 retina display, I was expecting normal resolution sprites to look at the very bad, exactly as in previous devices, so we could have the retina display to improve things, but is not, it is actually making things worst, which is not nice on terms of backwards compatibility (people tend to not care about backwards compatibility when I think it's very important...)
In my case I did spend time polishing my pixel art sprites, and they did look perfectly on pre iPhone4, I managed to change the antialias and stuff to look perfect, no blurry, no lines between tiles,... But now when I try the game on an iPhone4, it looks blurry. Which in a way I don't understand, if they are now using like 4 pixels where we had one pixel before, I don't understand why it looks blurry.
I don't think there is much we can do in terms of code right? Apart from creating a new set of graphics.
Anyway, just sharing my frustration and wanted to know some other comments on this.