How many apps are in the iOS App Store's top 200 lists? That might seem like a silly question: 200, duh. But even a quick glance through the list shows that they aren't all unique. The most popular app concepts have multiple top-selling implementations competing.
I was curious just how much duplication there was, so this afternoon I sat down and figured it out. I grabbed a copy of the Top 200 iPhone Paid Apps list at around 2:30pm, and categorized them all. The list is always changing (these days, it seems to update at least every 5 min), and there's no one correct way to make the categorization (you could lump or split more). I grouped all games and game-like entertainment apps (Pocket God and the like) together. A categorization of games might be interesting and they are a huge part of the app marketplace, but I don't understand them well enough to know which might be groupable. With those caveats, the answer is:
There are 46 unique non-game apps and 108 games.
That's even fewer than I expected. Emoji extenders are the most repeated app with 8 implementations. If you're a good icon designer and marketer, it might not be a bad idea to throw your hat in the ring. After that come photo editors (5 apps, including PicFX, Color Splash and iPhoto) and download managers, photo booth apps (Fat Booth and friends), and map replacements with 4 apps each.
One thing that stands about the results is just how popular apps replace or extend a built-in app's functionality. Four map replacements (most do turn-by-turn navigation), 3 camera replacements, 3 clock replacements, 3 weather forecast apps, as well as music downloaders (3) and radio players (1) which are partial Music app replacements. There's good money to be made if you can find a new twist or a way to extend one of the apps that came with your iPhone.
Here's the full table:
This is a pretty superficial analysis. There's a lot more that could be done, from categorizing games to looking at the difference between free/paid/grossing lists, to looking at popular apps within a category and comparing category diversity. I may take this further, and if I do, I'll update this post with links to my findings.