While I would agree that Company of Heroes is probably the best RTS I have played from a technical standpoint, I still have to say the best RTS I have played from a gameplay and 'fun' standpoint is Age of Empires III. There's just so much variety, so many classes and the improvements such as the card system and the unique units made the game better unlike most other RTS games.
But I completely agree that Company of Heroes is most likely the most balanced and best RTS I have played. I like both equally. And unlike Age of Empires III, the Company of Heroes community is still around and people still play the game. Hopefully it won't suffer the same 'sequel' effect of AOEIII.