How many companies make 2.6B/year in profit? Rather, how many startups sell for over 1B? Comparing it to another gigantic business is missing the point in the same way that comparing it against ads is. Google has had many giant successes that only appear small when juxtaposed against unimaginably enormous successes.
Consider that Google offers the operating system for free, the software for free, and only charges OEM for optionally including Google's software on their phones, and only recently began selling its own phones...$21 billion of profit is pretty damn big.