My idea of a successful "app" store would probably be Cydia, where developers are not rejected with dubious copypaste rejection letters, and where you can pretty much find anything Apple's app store has, but for free. That's a success, for the user, anyway.
Then go to Android or Windows Mobile. Have you even used those operating systems before?
Windows Mobile
WM sucks because there is no central place to find applications. Instead they are scattered all over the internet, and you need to spend a long time searching to find anything that sounds remotely useful. Then, once you locate this useful app, you install it and realize that it looks like it was coded 20 years before iPhone apps were and runs like garbage. That summarizes Windows Mobile.
Android
Android has potential, but thats it. The marketplace contains hardly anything that is as good as what the iPhone has, and the ability for Android apps to run in the background, at startup, and in the task bar causes your device to grind to a halt. If you want to find unrestricted Android apps, you need to enable 3rd party unsupported software which carries a warning itself. Then you need to do the Windows Mobile song and dance by searching the internet for the Android app you want that wasn't able to make it in the Android Marketplace. Once you find it and install it, you in many cases give this unsupported 3rd party app free reign over your phone and its content. Fun.
App Store
Centralized location to find great apps. Yeah, there are some that get rejected for bogus reasons, but that is almost never the end of the road. Apple is run by humans, the app review process was created by, and is operated by humans. What does that mean? There ARE chances for error. Thats the way the ball bounces.
*Cry* There are no clearly documented policies on rejection *Cry*
Quit crying you baby. How can you expect clearly documented policies when there are constantly new types of apps being submitted? The second you write a document saying "X, Y, Z will get your app rejected" you will get an app that doesn't fit into X, Y, or Z but still should get rejected. So what do you do? The policy never states that the app should be rejected, but you know that it contains content that *should* be listed in the policy for rejection but isn't. If you reject the app even though the policy doesn't specifically state those grounds for rejection, you could have a lawsuit on your hands. If you accept the content because the policy says so, even though it shouldn't be accepted you are lessening the quality of the store.
So what to do? Don't make a policy. Have an internal set of loose guidelines and tell the reviewers to look out for certain things. Alert devs if there is something that should be changed. This is the best way because applications always throw something new out there. Eventually, Apple will create a clear cut policy. Until then, deal with this.
Based on the size of the app store, its obvious developer rejection is NOT dominating the dev program. But it is the vocal few that spin this way out of wack and those unable to think for themselves read a developer sob story and think "ZOMG, this must happen to ALL devs!!!111!" Well guess what, it doesn't.
Human error, its a fact of life. Get the h*** over it and weather the storm if you want, otherwise MOVE ON TO SOMETHING ELSE.