A "large scale" real time strategy game set in a futuristic universe.
Its the future, the Earth Empire, ruler of the known universe through a quantum gate network has collapsed under the events that bring forth the Cybran Nation and the Aeon Illuminate. From the ashes of Earth Empire the United Earth Federation is formed to prevent total extermination of humanity. The Infinite War begins and its up to the player to lead this fight to an end!
This is somehow the plot the game follows. There's 3 factions in the game as described above, featuring different campaigns and endings, giving the game a very good single player experience and re-playability value. Saying that i must admit that the factions are quite similar in game play even if each one focuses on different tactics at the end (e.g Aeon may have better naval capabilities or different units).
The game play is focused around the Armored Command Unit (namely the supreme commander) which is the only unit the player controls at the beginning of the game or scenario. The ACU can be transferred through quantum gates anywhere in the galaxy it needed and through the blueprints it stores can produce an army from the planets resources through the classic RTS formula of resource gathering->structure building->unit building etc.
The resources the game needs is Mass and Energy (What? Its the same? Nah! Einstein sits corrected!). Mass must be gathered through mass extractors from specific spots on the map while Energy from energy generators anywhere. Later technology allows Mass production from Mass fabricator's which require vast amounts of energy. There's also the option using the engineers (you know the peasants!) to gather mass and energy from debris or forests.(useful also to "clean" map areas).
The structures the player builds belong to 4 tech levels (or Tiers in-game) and as you suspect the first is the starting one with basic structure and unit production and as the player progress to tier three he can built advanced stuff as shields and units with firepower to overcome any defense. The fourth and final tier is called experimental and generally allows unique structures with ... unique resource requirements.
All that is done in a rather impressive and detailed theater of war which varies from deserts to ice-covered land masses and seas. Everything is very detailed and good looking. The game engine allows zoom from inside the action to full strategic view where the units replaced by icons. (to give you a rough idea, its like having the minimap fullscreen). This overwhelming sense of "big-war" is covering some of the game's weak points tho. The UI is not so impressive featuring semi-ugly icons. The game is ambitious but hard, it takes things seriously and some unbalancing things make the game a bit of a struggle ... a bit of exhausting! It also can be quite time consuming. Mind you, this makes the victory something to be proud of and not just a way to next scenario.
As a conclusion:
Supreme Commander is an ambitious game which ironically features stuff known to everyone and mechanics that will remind you of something, even if you haven't seen Total Annihilation before. The large scale and hardiness put together with a great A.I. give the title a serious approach to war even if the appearance of gigantic amphibious robots and tanks and spider-like vehicles may sound a bit of "funny". Also worth to mention that through numerous patches the balance of the factions have been improved, even if lots of multiplayer gamers are still complaining about it. Patches also claimed to improved the high CPU requirements (it uses multi-core processors).
Supreme Commander looks like an achievement in gaming and maybe it is. Worth seen and played by anyone in my opinion, casual gamer or serious RTS fan.
The stand alone expansion Forged Alliance that followed is probably your best choice as it features one more faction and lots of new units.