Supreme Commander is a ripoff of CnC3 except its a total clusterforget.
How is it a rip off of CnC3? The only things it has in common are typical RTS features, none of which are original to the CnC series.
If by clusterforget you mean, a well balanced brew of unique units in huge maps (large enough to actually implement strategies) with a decent number of units, then yes, Supreme Commander is a clusterforget of awesomeness.
What makes SupCom better than other RTS games of it's kind is 1) the shear scale of the game and 2)The fact that you actually have almost complete control over your units. Plenty of different orders, stances, etc to choose from. The queue system is especially useful for base building and controlling factories. The ferry system is a great way to move slower units across the map.
I realize that since you are use to the dumbed down nature of CnC3 it might be a little too much for you, but that's OK.