This has been somewhat of a pet peeve of mine, the fact that Google Play and Apple Store app rankings are based purely on app downloads as well as user feedback (stars, comments) in order to reward and provide for greater recognition. Since the start of both app stores, the structure hasn't dramatically changed, albeit we have seen some minor changes, including algorithm changes to reduce fraudulent rankings.
Whilst I am not adverse to the notion of ranking based on downloads and rate or trend of downloads, there are two additional factors I believe would aid in creating a more accurate representation of app popularity, that Apple would need to implement on a platform-level.
If Apple would be able to track not just how popular an app is via download rates, but to track how often an app is used, daily, we would be able to determine that an app maintains it's usefulness beyond the initial download stage.
An app that was not just downloaded during a popular marketing period, but gains more usefulness later on whilst on the user's device, being relied on daily should factor in recognising that an app is not just sitting dormant on a user's device or downloaded and deleted, but actively used.
Exit survey & Rating API Access
I've always had an issue with how users rate and star apps. Usually if you are doing a good job, you won't have many people going out of their way to go to your app listing and give you four or five stars and a comment, unless you really touched them .
Most times, if a user has had a really negative experience with your app they will go out of their way to make themselves heard. Now, this isn't a hard fact of mine, as we do see a lot of people that give good ratings, I just believe proportionally more negative experiences get a rating than positive ones.
Encouraging users to post positive ratings and comments has been a challenge over the years and the general best-practice is to prompt the user to rate at an opportune time. When a user has completed a task, during that short time of gratification, the user would most likely be in the midst of a positive experience, in which case the user would feel compelled to give you a positive review. Prompt the user too often or indiscriminately and that may not be the case.
What I would like to see in 2015 is for Apple to adjust this so that you have direct access through the API to provide a system RatingViewController, so you can add stars within the app and not have to exit the app. This adds for better usability.
Secondly, when a user delete's an app, the system should also provide an exit survey opportunity, an ability to provide a star and comment to let developers know that there is a problem with his or her experiences, in what is called an exit survey. This may not necessarily yield a positive review, in fact you will probably get a negative review, but hopefully, it would be a more constructive comment.