Just a couple of days ago, during lunch, I was talking about this game with two of my teammates. It had been my first contact with the RTS genre (which it arguably invented in its modern form) during my early teens, but they hadn't even heard of it.
Later I sent them a link to the Wikipedia article about it. One of them said "wow, this is the mother of all RTSs!".
The other one said "wow, this game is a bit older than I am!"
Mass market, yes. But Herzog Zwei for Megadrive was out earlier and was already a RTS. It was not very good (at least my memories of it are not good - playing with a gamepad was a nightmare) but it was already going in that trench.
As I recall, Herzog Zwei has a few key differences from modern RTS games:
1) The player fulfills the commander role by directly controlling a unit on the battlefield, not in "god mode". The commander unit isn't merely a stylized cursor; it also directly engages in combat.
2) No base-building or tech tree. The number, location, and capabilities of all bases are fixed.
3) No explicit resource gathering. Money is automatically accumulated based on how many bases you control.
You can go back further, the original Herzog on MSX had RTS elements, and 1984's Stonkers[1][2] for the ZX Spectrum was the first commercially published RTS (AFAICT). Whether it's sales constitute mass market success is a different thing.
Dune 2 invented the C&C/Warcraft/Starcraft style RTS though. Other games had RTS elements to them before that, but not like Dune 2. And certainly not to the extent that subsequent games tried to copy their successful format.
I'm not sure I follow. I linked to a video of an RTS game from 1984. Stonkers (AFAICT) invented the RTS. It didn't have RTS elements. It was an RTS, similar to Dune 2 and the others to follow.
Most of the successful games that copied Dune 2's format were written by the same studios (Westwood for the C&C franchise, Blizzard for *Craft).
Early RTS reminded me immediately from Populous. But I guess it doesn't count in this case. Even if it uses isometric graphics aka "RTS graphics", it's bit different in game play.
Later I sent them a link to the Wikipedia article about it. One of them said "wow, this is the mother of all RTSs!".
The other one said "wow, this game is a bit older than I am!"
:_(