Google's jump into the hardware arena with self-branded phones began with the first Pixel phone at the end of 2016, and the company still has a ton of work to do.
In comparison, the Galaxy S8 and S8 Plus sold 20 million devices in around four months a year ago.
That's for both Pixel generations, mind you, and the year as a whole, although the number doesn't come straight from Google. Of course with a wider customer base you'll sell more phones. However, looking at the big picture, Google still has a lot of catching up to do.
Technically manufactured by HTC, the original Pixel and Pixel XL were the very first phones advertised as "made by Google", and El Goog began investing big money in the promotion of its Nexus follow-up efforts. While top devices from Apple and Samsung are widely available via all major wireless providers, Pixel 2 and Pixel 2 XL handsets can only be had through Google's online store or from Verizon (in the US).
It also certainly does not help the Google Pixel's cause that there are certain problems associated with the Pixel and Pixel 2 smartphones, including microphone defects and touchscreen problems. More countries, a better retail presence, and more carrier deals would be a good start.