Supreme Commander can be described in a single word: EPIC
Supcom redefines what a real time strategy game is. Many other RTS games like Command and Conquer for instance, each skirmish in that game feels like a battle, well, each skirmish in Supcom feels like it is a war! Now some people might prefer C&C's short 15 minute rounds but I don't think anything beats having all out warfare with your buddy for 4 and a half hours. I was looking at how many kills I had gotten in one of my online games and you know what it was? I had racked up 2984 kills in a one on one game. That is craziness! As far as graphics go, Supcom is stunning, some people will tell you, "Company of Heroes graphics are way better!!(insert more fanboyish comments here)" but who cares if they are better? Supcom's graphics are crisp and insanely detailed. This can be a problem though, since I found myself more than once simply watching the battles rather than giving orders to my units! The one problem with Supcom is that the difference between the factions is mostly cosmetic. Each factions plays similarly although there is enough difference between the factions that you will pick a favourite. The place where the factions differ the most is in experimental units. The aeon have a gigantic robot with a quarter of a million hitpoints, a flying saucer with an Independance day style Beam of Death, and a battleship submarine. The UEF have a mobile factory with four sets of three cannons, 2 anti-air guns, and close range guns, a submersible aircraft carrier, and a strategic artillery installation that can shoot anywhere on any map. The Cybran have a spider bot with a powerful beam weapon, a super powerful gunship, and a mobile rapid fire artillery unit.
Any of you remember a little game called Total Annihilation? If you ever liked that game, then supcom is guaranteed not to dissappoint. If you like RTS games in general, same deal.
Overall I recommend this game to anyone who likes RTS and has an above average computer with Dual Core.