I haven't used ios for a while, but the ones I can remember having problems with are X plane 9 and bloons tower defense 4. There were many others, but I can't remember what I had on my iPhone. They may be fixed now, and if they are that's great, but I know it was a problem when I had my iPhone.
It's partially the developers fault and partially Apple's as well. Seeing the apps wouldn't scale on the iPhone 5, the developers should have fixed the apps. That's a no brainer. But they wouldn't have that problem if apple thought ahead and made the screen the proper size for the apps to scale. All they did was stretch it vertically, the width is still the same. If they made it wider, they wouldn't have this problem.