I just opened up Angry Birds Seasons today and the graphics looked blurrier than usual. I don't know how reliable a screenshot is but here is one I took and you can see it looks blurry. (Also, the image came out at 800x534 pixels, but apparently the Retina display is 960×640.)
I recently upgraded from an iPhone 3G to the 4S and transferred all my settings directly, so I wondered if the games were perhaps still trying to use the non-Retina display. However, I hadn't noticed any problems with the games until today, and another game I've downloaded since the upgrade also doesn't look quite right today.
What could be the problem here?