That comparison doesn't really work, because MSFT had an effective desktop monopoly. By contrast, Apple is a minority player in the mobile market.
>They should be FORCED to have an open platform,
Just because YOU want this doesn't mean the Apple users want it. I'm utterly content with a single, curated-by-Apple app store for iOS. I like the stability it affords the platform.
I'd never accept it on a general-purpose computing device, but for my phone it's perfect.