What’s weird about a Skill is that it’s a combination of two things — an application that has some interactivity and content that needs to be consumed. The Skills that seem to be the most interesting either offer some real utility or provide something new with each interaction.
Song Quiz and Jeopardy! are two Skills that have thousands of five star reviews. They offer something new everyday and allow for content from the past week to also be consumed. The Skills that are used most however are the utilitarian ones — play music, set a timer, turn on / off the lights. These ones are native to the Alexa interaction.
It would seem for those looking to hack making a top Skill, one of the approaches is to look at piquing user curiosity by having constant fresh content. It’s not easy — and maybe that’s what separates the wheat from the chaff?