Expectations for Tim Cook were almost impossibly high when he stepped in to replace Apple's visionary co-founder in 2011. He inherited a company on a blockbuster run, after Steve Jobs returned and revitalized the Mac, launched the iPod, and oversaw the launch of the iPhone.
Now, after 15 years in the CEO role, Tim Cook is stepping down. He's replaced today by hardware leader John Ternus. Over the course of Cook's tenure, Apple accomplished a lot, with the launch of plenty of new products, features, and services that the company just wouldn't be the same without. There were plenty of ups and downs, but Cook helped cement the company as one o …