RTS: Supreme Commander is so good, it has actually ruined my experiences with other RTS games.
For instance, I was playing Age of Empires 3 the other day and I got really annoyed that you can't even do simple things like set which way a unit faces for move orders, or set cannons to be defensive.
Supreme Commander doesn't have as many different unit types as some RTS games, but the depth of the controls and the well balanced nature of the game make it one of the best RTS games ever made.