Which came first, Android or YouTube?

YouTube came first, by 3 years. The domain was registered; the first video followed in April.

Side by side

Android

Android as a company was founded in October 2003 — four years before the iPhone — originally to build an operating system for digital cameras. Google bought it in 2005 and the first Android phone shipped in October 2008, fifteen months after the iPhone went on sale. So Android is older than the iPhone as a project and younger as a product, which is why the question needs the distinction stated.

YouTube

The youtube.com domain was registered on Valentine's Day 2005, the first video — "Me at the zoo", 19 seconds of a co-founder at San Diego Zoo — was uploaded on 23 April, and the site opened publicly in the winter. Google bought it in November 2006 for $1.65 billion, about twenty months after the domain was registered. It is younger than Facebook by a year and older than Twitter by one.