Mobile apps started way before the iPhone and the App Store, but the iPhone has come, got everybody on the mobile app roller-coaster and moved through the 100,000, 500,000 and 1,000,000 apps barriers. Its true there is a lot of duplication, but that is just a bit like saying that there is a lot of duplication to the over 7000 restaurants in London... a lot of them are Italian, French, Indian, etc.... but so what - what a choice! The App store has mostly had a lot of quality as well as Quantity.
Quality Apps over how many apps does an app store need
And that brings me to the most important point, I have helped build a few App stores in my life, from mass market to very high-end, and somewhere along the line the 'how many apps do we have' becomes a way more important Key Performance Indicator than it should be. What is important is to realise that 50,000 or even 1,000 apps in your app store are not the issue, as most people only use a few mobile apps at a time, even if they download a lot, and even then we are talking dozens or hundreds, thousands at the very, very most, so how many apps do you need?
Mobile apps that matter
Well it partly depends on customer diversity - the iPhone has a very diverse base of customers, each with their own tastes, which requires a wider range of apps. The key is however to an ecosystem is also to engage people to use the wide variety of apps and build more, which keeps people in a loop, both for the app store choosing apps, to the app developer - however very few get it right, and quality will always win over quantity. These for me at least, for the iPhone, are the apps that matter over time: