Hi Mark,
A pageview API is coming out soon that will let you find the top 1000 articles for any period of time since May 2015. By soon we mean within a few weeks, an announcement will go out to this list after some initial testing.
To get the top 2 million articles you'll have to write a research proposal and get one of the folks with access to volunteer to do this. This list is probably your best chance of finding someone like that, just let everyone know what you're looking for and why. (The reason this wouldn't be available via an api is because it's a lot of data and not likely to be useful in more than your case).