The Total Annihilation sounds were excellent. The mechanized whirring of a unit going into action, the heavy thud of artillery, the high pitched engines of jets taking off were an audio joy. Dark Reign cannot boast sounds like that but in all fairness they are far from being a total bust. However, it does have some uniqueness about it when you get into the air power armaments. What makes for a thinking man's game is the characters.
Behaviors also can play a vital role such as scouting and search and destroy.
Of course, you must build a base and it doesn't hurt to provide some strong defenses early. You can not afford to over estimate your ability when building something, as resource management is incredibly important. You have to gather the vital resources for your armada, many times while under enemy attack. Water is a big deal in Dark Reign. You grab it and sell it to finance your war machine.