Company of Heroes combined intense military action with rich strategic complexity back in 2006, and it can definitely use an HD remake to improve its already advanced (for its time) visuals. Company of Heroes stood out most evidently because of its subject matter, filling a niche for a more modernized RTS experience. The game allowed for unbelievably detailed military decision making, allowing you to develop your tactics with unbelievable precision.
Soldiers behaved realistically, meaning that you could focus on the overall objective without having to worry about the movements of individual units. Their advanced AI interacted with the environment as it crumbled around them, reinforcing the tension of the dynamic battlefield that is being torn apart as you fight. An HD remake would allow for improvements to an already sophisticated environmental system that can be more in tune with current standards.