h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Some important RTS games that seem to have been left out of this article are:

Dark Reign, Activision, 1996ish. First game to use elevation on terrain. Well done engine, but the game itself was far too difficult and never recieved much publicity.

Total Annihilation, The Core Contingency, TA: Kingdoms. All by Cavedog. The conversation on TA has all the details.

Dogs of War, Dark Reign 2, Battlezone, Battlezone 2: All were RTS games using a 3D engine, similar to that of first person shooters, yet using a real time strategy style of game play. Also, I'm not sure if Myth: The Fallen Lords counts in this genre, but it was a RTS game in 3D. The only difference is that in Myth there was no base building or resource gathering, and the whole strategy was in how you used the forces you were given.

The author also fails to acknowledge more recent games such as Shogun: Total War and Homeworld.

Homeworld is important because it was one of the first fully 3d RTS games, with "360 degrees of freedom" (funny, I remember them saying that about Descent ) and therefore involved a significantly different gameplay style. Shogun deserves a mention for its emphasis on tactics and military formations, something that most other RTS's had only lightly touched on when it first appeared.

Homeworld isn't true 3D because it still has a clear concept of 'up' and 'down'. It's easier to issue orders with horizontal movement than vertical movement, and this kind of thing really makes a difference. Unlike descent, which was genuinely 3D. To my mind, if you're going to make a space game, you really ought to make it properly 3D - otherwise you should stick to solid ground...

This is a bit harsh. Descent might have been 'properly' 3D but it was set in a situation where you are always responding to walls of some form. Also, these are often parallel to other walls so they're not totally 'freeform'.
Homeworld DOES have a built in horizontal level but to my mind - having played both extensively (and poorly!) - it is effectively a lot more 3D than Descent.
I soeak from a situation of having played Descent a lot more (and with more success!) than Homeworld.