Not quite an RTS, but Arma 2 I am playing atm is close. It is a 4 man US marine recon squad and it's virtue is an all out effort for realism. Downside (tho not for me, this is good imo) of this if you get shot, you are down or dead...no health bar
Medics can patch up non-fatal wounds if they can get to you in time.
Later levels (I am approx 11 of 15 through the campaign atm), has you controlling troops, APCs and Armour. Driving a BMP cross country to capture an enemy village watching out for AT infantry is good fun. The array of weapons and vehicles is impressive, I havent got to use helicopters yet but they are in there. The computer AI is good, it wont frontal assault it will try to flank. If you are in a building, the troops dont run in to be bodies stacked at the door like many others. They surround and wait.
To come I think is the command and control of units, like a proper RTS, but not really tested this.
If you want to play around with weapons and armour (modern) with max realism without getting dirty, this is the game for you - but it is hard!