
From the WRP homepage (http://wz2100.net/):
I'm really glad that I found this before going to buy C&C3. If you can look past the graphics, This game is amazing. The single-player campaign is pretty good, but my favorite thing about this game is the skirmish battles. You can play against as many as seven other computers. You can form alliances with them, have fixed teams, of just play every man for himself. You can adjust the difficulty level of each team, And you can even play one-on-one on a map that was designed for eight different teams total.In Warzone 2100 you command the forces of "The Project" in a battle to rebuild the world after mankind has almost been destroyed by nuclear missiles. The game offers campaign, tutorial, multi-player and single-player skirmish modes. An extensive tech tree with over 400 different technologies, combined with the unit design system, allows for a wide variety of possible units and tactics. Warzone 2100 was created by Pumpkin Studios, published by Eidos Interactive and is currently developed by the Warzone 2100 Resurrection Project.
And you don't just tell your factories to build units.
You actually design each unit.
There are about a dozen different body types to choose from, which you will then add a type of propulsion (ranging from wheels and tracks to hovercrafts to VTOL propulsion <3), and finally, a weapon. (ranging from the simple machine gun to archangel and scourge missiles to rotary howitzers)
In the place of infantry, you have cyborgs. Unfortunately, they aren't as customizable, but they are a valuable asset, as they can be loaded on to a transport and flown just about anywhere on the map.
The online mode seems to be... broken. (?) But the game is under development, and hopefully they'll get it working. The game isn't perfect, and it has a few bugs, but it's a heck of a lot of fun to play and the computers pose a good challenge.
The game is open source, and there are fan made mods and maps also available for download.
You can get Warzone for Windows, Mac OSX, and Linux as well (I think). If you try it out, I highly suggest the tutorial, even if you've played C&C, because Warzone is quite a bit different from C&C.
I highly recommend this game if you like RTS'. Check it out.