Not trying to diminish his work, but hoping to provide some perspective. It's important that people understand the vast collaboration behind the project and the numerous voices that have built it up to what it is today. If one person was responsible for most of the content, it would be nowhere as diverse as it is.
It is always hard to measure these secondary and further effects. The best way to determinte the value is a market with independent actors. Thought experiment: imagine Wikipedia edits were paid in some currency. Doesn't have to be monetary; it could be e.g. karma. How much would he have gotten per edit? Sum it all up: that's his contribution.
One thing is for sure: it's more than just a motley of typo fixes. He has, indeed, added a lot of value to Wikipedia, albeit probably indirectly, and, thus, helped people through school.
But the nature of Wikipedia means that entropy/rust/rot is a very really thing - and the wikignomes that tirelessly keep articles together in the face of endless silly vandals and clueless people "just trying to set the record straight" are big part of that. Internally there is some recognition in the relatively new "Thanks" feature - and the "barnstar" business. However, just as with Steveen Pruitt, I suspect that the main driver for editors is being able each day to make the world a slightly better place.
And, Wikipedia happens to count those edits separately even if the editor applies the fix to multiple articles at once as a single action. <-- This is my self-assessment though, I could be wrong!
3 millions edits, however, is still an astonishing accomplishment, even taking this into account. Edits that don't require any human thinking are usually done by bot accounts, and few of them have that many edits.
User Aka in the German Wikipedia follows Steven with only 30,000 edits behind in the main namespace.
 some statistics:
English Wikipedia: https://stats.wikimedia.org/EN/TablesWikipediaEN.htm
German Wikipedia: https://stats.wikimedia.org/EN/TablesWikipediaDE.htm
You can step off that high horse now.
Just for clarity, I think you meant the Foundation trilogy. Asimov wrote an awful lot of books, and more than just the one trilogy. (Also, there are more than three books in the Foundation series, but that's a separate point.)