This will hurt Apple in the long run.

Soon app innovation will stifle because only a very few companies are making money. Indie/mid size developers will stop working on innovative apps and start working for bigger risk aversing boring companies.

Biggest reason imho is that these top 25 are one big self fulfilling prophecy: A top 25 position guaranties big download numbers. And to get there you need either a collection of apps already out there for cross promotion or buy lots of ads and installs.

Switching to a metric that indicates quality much like engagement measured by # sessions or # minutes use/month will make quality apps stand out much more.