Any decisions that would affect their trajectory will get a ton of deliberation from a lot of smart people; i.e. there wouldn't need to be a ton of input or ingenuity from the CEO to see returns like those from Apple, imho.
Not to say that Cook isn't great or that it wouldn't be difficult to achieve that success.
I believe most of Apple's value is from delivering a high degree of consistency and polish; owing to its culture of relentlessly developing the UX of their products.
Therefore the CEO's primary roles at Apple would be to maintain that culture, steer the ship into new segments, and discern when the public will care about those segments.
I think Cook has done a decent job of that.
Making it all possible with RnD and supply chain is another story, but also where Cook is known to excel so maybe I'm underselling him. Jobs had Cook so presumably Cook would find a Cook if he weren't Cook.
I don't know much about Microsoft but Balmer was definitely taking over a different beast than Cook.
But that sure didn't last.
Of course you can argue that the wrong leader would have torpedoed the company.