As in flash games? Then I suggest: Shadez, Warfare 1917, Prince of War, Prince of War 2, Tainted Kingdom, and Subterfuge. (there are a few more I'm not mentioning, that I can't think of at the moment; you can check my account for those, if you want.)
If not for flash, then Battle for Middle Earth, and Age of Empires. There are also a bunch of awesome Space/Sci-fi RTS's that I can't remember the names of! Hope I'm of servive!