I love settlers, but only the first three. The seventh one is awesome too, but the DRM is killing me. So, I will recommend the seventh one if you can stand the always online DRM issue. [In my country, internet bandwidth is so much more expensive, and harder to get]

I loved starcraft, 1 and 2, and I played all of the warcrafts to death except 3 and frozen throne. I didn't care for them as much. Too much focus on the heroes. But back then it didn't run well on my computer maybe i will play it again.

company of heroes

Warhammer as in Dawn of War? Cuz that's a game I'd suggest. Another game RTS I'd suggest is the Red Alert series. I love the politcal satire. Namely Red Alert 2 and 3.

A game I haven't noticed mentioned here is Cossacks, which can be quite an epic game... its like Age of Empires (only a couple centuries ahead) but with a scale more in line with Supreme Commander.

http://www.youtube.com/watch?v=s9BsCOz2QOY&feature=related

http://www.youtube.com/watch?v=xfRvEl9x0-M&feature=related