It depends why and how the sales are happening.
A horizontally integrated platform in which a universally-licensed OS is spread out to everyone who can slam together a box, will experience substantial sales for reasons far different than a vertically integrated platform that is highly differentiated, vetted, comparatively more expensive, with a closed-licensing model where the focus is on differentiation and User Experience (and not pushing massive volume on price.)
You can certainly measure innovation by sales, but if you don't understand your measure (sales) then you'll come to wrong conclusions.
Apple can sell 100 units and Google can sell 100 units via x-number of OEMs. They both sold 100 units. However, there are vastly different forces at work here.
What's happening with Google/Android is your typical OEM-based horizontal business model at work. Virtually any OEM, provided they push enough volume, can outsell Apple by sheer force of numbers and nothing more. And these OEMs *combined* - even if they're ZTE or Huawei, can pinch off and push out even more.
At one point Nokia far outsold Apple with all manner of flotsam and jetsam - a lot of it essentially low-end commodity-ware. It's quite something else, however, to gain the share Apple has with essentially one or two models that run an unlicensed OS. That one phone had better be amazing, and the numbers bear out that it is.
Not all forms of "success" are equal. Google/Android's is rather weak in comparison to Apple's. OEMs pushing volume is nothing to really boast about.
Look at PCs today. Then look at Macs today.
Anyone can pimp out an OS to OEMS and sell tons of $400 eMachines. But what is the consumer actually getting?
We know what they're getting with a Mac, though. Each and every time.
https://www.macrumors.com/2011/09/20/...secutive-time/
Similarly, look at Android phone sales vs. iPhone sales. Certainly, Android manufacturers combined and even some of them on their own far outsell Apple, especially given that even some of them on their own have a portfolio of 40+ devices, some of them decent, some of them total junk.
I wouldn't wish a ZTE Blade on anyone, but
ZTE actually commands a large portion of Android share. ZTE far outsells Apple. Impressive? Not really.
Because here is what is *actually* happening - here is where the rubber meets the road:
https://www.macrumors.com/2011/09/0...rankings-of-smartphone-consumer-satisfaction/
http://cdn.macnn.com/news/1110/androidfragmentation-lg1.jpg
An unweeded garden is an unweeded garden, no matter how large. And it will show, one way or the other.
So getting back to your question: yes, you can certainly measure innovation by sales, but not all sales are created equal. Understand the measure you are using.