iOS isn't customizable, and (its current version) cannot be rooted.
So what is it, if not a huge hit?
Rootability and customization is primarily an entertainment for geeks frequenting internet tech forums - yet hugely overrated for the masses. The vast majority of people can or choose to live without great customising their devices. If you don't consider "getting Apps" as customization, that is (though Apps somehow are way of customising a phone).
That being said, there's still some lack in app availability on WP8, yes. But the OS is fine.
Microsoft chose a similar route as Apple with Mac OS X: offer less customization while going for a more consistent and elegant interface and operation.
So which "everyones" exactly use octo-core processors?
Or quad-cores, for that matter?
Apple doesn't. Their A6 used in the iPhone 5 (their current flagship phone) is stinkin' vintage dual-core (!) CPU. WP8 runs very well on high-end Nokias, as does iOS on iPhone 5.
Again, that being said, yes, both offerings won't impress people drooling over sheer numbers - but hey, let these people be victims of marketing.