Supreme Commander can be considered a great strategy game.
First of is the gameplay. Its just like your average strategy games. Your controlling a camera overlooking the battlefield. You build units and buildings and do some research to have more powerful weapons or units. However, one big difference of the game is its scale. The game's map itself are big and you can create a lot of units in one single game but too many units at once in view can cause the frame rate to drop, including when there's too many in the game even when they're not within your camera. There are three factions within the game and they have different kinds of technologies and feel balanced. The enemy itself can be smart within the game though it also depends on the difficulty.
One problem within the game is how slow it takes for a player to get a good start up in a match, especially in multiplayer. Apparently, it takes some time for you to build a base at the start and getting a good flow of resources just to be able to create buildings and units steadily just add more to the complication. Basically, the first player in multiplayer to get a decent base started will probably win, unless the other player somehow catches up. However, in the later missions in the campaign, you probably already have a base so there's not much problem there. Another problem in the game is the pathfinding. Sometimes, you send a group of tanks to the an enemy battalion. There is a steep mountain your troops can't pass through. Sometimes, what's they will do however is try to go straight through the mountain as if it wasn't there, even though they can't, rather than find alternative paths and this sometimes holds true to the enemy. This doesn't happen often though but it depends mostly on the obstruction.
The graphics of Supreme Commander look real nice. All the units look detailed though they look a bit bland in low settings. This holds true to most parts of the graphics of Supreme Commander. In order to enjoy it in its highest, you need to have a powerful computer as Supreme Commander has high requirements which is probably because of its large scale. Like what I said above, the game itself starts to have low frame rates when there are too many units on a match at once.The game itself will be slowed down automatically to maintain stable frame rates and you can't really do anything until your computer can be able to handle the game. Again, this won't be too much problems for those with powerful computers.
For the sound, the game does a nice job of it. All units have sounds that appear to fit them when they're moving or attacking. Clicking on buildings itself triggers a sound specific to it and it they're nice. The music also is great and appears to depend on the map or situation on the game.
The game doesn't have much replayability in the campaign though its single player and multiplayer will probably occupy you for a while, that is if you are patient and your enemy online is patient itself.
Overall, Supreme Commander is a good strategy game mostly because of its large scale and good graphics. However, it's problems sometimes frustrates you when your playing but they don't always happen.