The more content they can get under your nose that you like, the more content you buy, the more the app devs make, the more Apple makes and the more desired the iOS store becomes.
This is why Netflix and Amazon spend millions on their reccomendation engines; same idea here.
I think you probably knew this though. I am only solidying the point that inside any app stores environment, it is the job of the owner of the store to markwt the content effectively. Outside the store, anyone can do anything they want.
Not only do my Genius recommendations rarely change, the hit rate of things I actually want to play that is recommended to me is something like 4%.
Google seems a bit better at this, but Apple is awful at this... like "Dear god just acquire some company that is recommending toothbrushes and adapt their algorithm" bad.
At least from a user perspective.
I strongly believe that it IS Apple's job to help get apps in front of iOS users because it's an ecosystem that prides itself on better apps. I agree that if Apple gave developers' a better way, to hell with bots.
As for a third party solution, people have tried. People have tried to create websites to rank apps, but they just don't work without incentivization (which to many of you, means misleading the end user.) Ask yourself honestly. Would you yourself log onto a site every time you try an app just to rate it?
Let Android start catching up revenue-wise and I suspect Apple will find they can have a UI expert look at iTunes and fix so many of the glaring warts.
I think there's room for a third party solution. A website where you can rank apps you like, and it recommends other ones you might like could work. There's lots of potential options for app discovery businesses, I just don't see how Apple can get into it at the level a good third party solution could.