Google highlights what it thinks an app should be:
Many mobile app stores have an editor's choice section that spotlights the latest and greatest titles. However, Google wants to go one step further. It's launching an Android Excellence section in the Play Store that highlights the apps that offer "incredible user experiences," adopt Google's "best practices" and are fine-tuned to run well on phones around the world. To put it another way, these are the apps that Google wants to see -- you should have a good experience, of course, but they'll also show the way for budding developers.
The initial app mix includes more than a few familiar names. Evernote, Pocket and Runtastic are among Google's favorite general apps, while it's fond of games like Hitman Go, Pac-Man 256 and Star Wars: Galaxy of Heroes. And you can expect to see those apps hanging around for a while. Where editor's choice sections can change frequently, Google plans to update Android Excellence once a quarter. If an app makes it to Android Excellence, you'll know it was a carefully considered choice.
Source: Android Developers Blog