According to Microsoft, the criteria for selection are:
- Functionality - Strong performance and stability, intuitive, and easy to navigate without instructions
- Utility - Drives repeated and consistent use, originality and innovation, and strong visual impact
- Enjoyment - "Make your users say 'wow'", meaningful use of Windows Phone design features, and apps that take advantage of cross-platform synergy for platforms like Windows Phone, Windows 8, SkyDrive, etc...
More details on the selection criteria are on the Windows Phone Team blog. If you see the feature let me know!
Check out What I Eat on the Windows Phone Store!