Sorry to be an ass but your post was basically "Supreme Commander rocks because it has great graphics, oh and did I mention it has great graphics?". An RTS is all (or at least should be) all about gameplay, this is basically why Starcraft II has those graphics (which don't look demanding of a good comptuer at all) because then more people can run it and they are most probably focusing on gameplay.
This is why Blizzard RTS are so good.
RTS = Great Gameplay, Story Line for Single Player Mode
Shooter = Graphics, Realism, Unrealism, Seamless Multiplayer
Role Play/Adventure = Story Line, Game Play, Graphics A Bonus
Those are the priorities in my opinion, feel free to amend as necessary.
Some of the greatest games ever made had those characteristics:
DeusEx (RolePLay/First Person) - Excellent Story Line, Good Graphics, Fantastic Game Play and Replay
StarCraft (RTS) - Top Notch Game Play, Excellent Single Player Story Line
System Shock 2 (RolePlay/First Person) - Excellent Game Play, Good Graphics, Good Story Line
Fallout 1/2 (RolePlay) - Excellent Story Line, Fantastic Game Play, Good Graphics
Monkey Island Series - Great Story Line, Tremendous Entertainment
and on and on and on...
Graphics alone can never make a great game, and from history, it can never break a great game. A lot of the dated games have crappy graphics by today's standards, but are still excellent games and frequently played - StarCraft for example.