Company of Heroes is the best: one or two you can't go wrong, the other ones either have too much macro manage, too much economy, too much random memorization, extremely annoying control setup, or any mix of these issues. Company of Heroes is a tactical combat RTS game at its heart, where the strategy is all in what and where, and not so much how many and when. Flanking, bait and switch, there's never a dull moment or a "buildup" phase to worry about either.
Combat strategy at its finest.