Looking over the data on Ars's article for a couple things in my wheelhouse:
Point & Click Adventures:
* Best I can find is Deponia at ~750k
* Best LucasArts seems to be Grim Fandango Remasterd at ~510k. MI2:SE is ~288k, DoTT is ~265k. Full Throttle is MIA.
* No Thimbleweed Park
* Nothing from Wadjet Eye
* Nothing from Sierra (nu-King's Quest is likely a flop as expected)
There is probably some confirmation bias but looking at the numbers, it's hardly surprising that Telltale went full-tilt into their current model. (The Walking Dead at ~2m. Wolf Among Us is ~1m and Tales of the Borderlands is ~500k) Or why "walking simulators" have come into their own finally. With some exceptions, most of the well known point & click adventures seem to cap out at around ~250k. That's pretty bleak odds. (Situation might be slightly better on GOG which has catered to fans of that genre for longer).
Might & Magic franchise:
Heroes of Might & Magic III - HD Edition at ~591k
Clash of Heroes at ~309k
No wonder Ubi put that franchise on ice :( Could be better on GOG or UPlay but that doesn't paint a good picture at least for the more recent games. Heroes V is sold on Steam but lacks achievement support.
And I'm pleased to see SolForge at #1000. Such a shame that game had to die.
Also it's a shame that Valve quickly closed this up. They had a good excuse when killing Steam Spy last time with the GDPR compliance. This time it's pretty apparent that they just want don't want people to know numbers.
I wonder if part of that is that it could possibly give some insight into how well they're doing financially. The 30% cut of every sale is one of the worst kept secrets in the industry, so if you can track the user numbers over a long enough period of time and account for sales + free weekends you could theoretically work out how much cash they're making in a given month. As a privately held company they probably don't want to disclose more than they have to.