Of all the silly little games I've played in the last month, I keep coming back to Crossy Road. It's not the mechanics: The app plays fast and loose with the Frogger look, but it's essentially the same movement you've played in side-scrollers for years. Step forward. Jump on a moving target. Jump to another moving target. Avoid the giant train. It's not the in-app purchase pleas, which are about on par in their annoyance with every other free-to-play game.
No, Crossy Road is charming. Which is odd, for a game that regularly cries out for ratings and in-app purchases. I usually detest games like this. They annoy me and then I delete them.