I'm guessing you haven't really looked in the Windows Phone app store.
There are more dedicated iPad apps than there are WP apps, and the app-to-crap ratio of Windows apps in GENERAL (Windows Phone, Xbox and Windows combined) is still higher than iOS or even Android.
Apple still has the advantage, I can guarantee you that. Why? Currently the iOS platform has the most sales per app (be it free or paid). iOS users have always averaged having more installed apps compared to the other platforms, and the iOS app store has paid more to developers than the Google Play Store or whatever Microsoft calls their market. Most apps start on iOS or get updated on iOS first because developers know this. I can tell you with our apps, we see 2-3x as many sales on the iOS app (despite the Android app actually being (slightly) superior to the iOS one).
iOS just has a larger market for apps, and I doubt that's going to change anytime soon.