I didn't play much of it as I didn't have my 360 for very long but definitely Halo Wars.

It really is a shame MS closed Ensemble, they really were a great studio that produced some of the best RTS games around.

I haven't played many RTS's on a console besides Halo Wars and Alien v. Predator: Extinction. So I would have to go with Halo Wars. 

1st was better.

Pikmin 2, probably replaced by 3 when it releases.

True that.

Yeah Halo Wars is a fun game. I believe that Ensemble could have developed a sequel that really nailed console RTS with the info and feedback from Halo Wars.

Civilization Revolution is awesome from the little that I've played

Does Fire Emblem count? If so I change my mind to that.

halo wars for sure. I was hoping for another one maybe with kinect integration

Civilization Revolution and Fire Emblem don't count, they are TBS (turn-based strategy).

For me: Pikmin 2 and Halo Wars.
Two completely different games very well done. Miyamoto vs. Ensemble Studios, console tradition vs. PC tradition. People often forget Pikmin 2 when it comes to console RTS discussions, but it's pobably the best original console RTS game created so far and showed again that Miyamoto is still one of the best console game designers.

Honorable mention: Little King's Story.
It has its flaws, but it's by far the most charming RTS/city-building mix I ever played (btw: think twice if you plan to buy the PSV port which will be released next week, I've read it has severe frame rate problems).