For those of you who like starcraft, you should try the demo for Dawn of war.
Blizzard when making their game took all their ideas from warhammer 40k which is exactly what Dawn of war is based directly off of.
Relic the creator of Dawn of war also came up with a revolutionary resource system which relies on taking and holding strategic points. It rewards aggresive players and controlling the whole map instead of just taking crystals and gas and turtling.
I am a big fan of RTS games and def have to say this one stands above all. It got alot of awards including game of the year.
link to demo.
http://www.fileplanet.com/contests/sept04/dawnofwar/