must have:
- Age of empires series (including Star Wars Battleground),
- C&C generals/zero hour,
- Red Alert 2 (stay away from Red Alert 3 it's rubbish - C&C tiberium is average),
- World in Conflict
- CoH opposing front - great expansion
- Commandos (1 to 3 only, forget Strike Force): not typical RTS, you have small squad and it's really immersive, really need to take your time and think about your moves.
can also try:
- Rise of nations: very cool units but world map thing isn't great, upgrading civs is different but OK
- Cossacks: if you like huge armies w/ +1000
- Joint Task Force: pretty damn good actually, not typical RTS but quite fun nonetheless. I recommend and can be played at your own pace which I like since I am not into blitz.
- Act of War: pretty cool units, game is definetly worth a try, but somehow it isn't one of my top games
- Starcraft: excellent. would be in "must have" except it has aged a lot now + can only play it 800x640 res