Captures some of the best things from Left 4 Dead, and presents it in a distinct game where zombies are replaced with SWAT troops.

The game itself is amazing fun and looks gorgeous; but it has some of the shoddiest multiplayer netcode I have ever seen (even a year after release), so trying to get a game going with some friends can be quite frustrating.

SupCom2 is one of my 3 favourite RTS games along with Starcraft 2 and Dawn of War II.
SupCom2's strength and focus is overview, managing base and resources, and big armies of expendable units. It is probably the most strategic of the 3, so matches tend to have much bigger scale and last longer.

Compared to DoW2 and Starcraft2, there is drastically less faction diversity and thus drastically less focus on the unit composition of your army.
I think each of the 3 games are different enough games to not compete for the same niche. DoW2 has more focus on manouvering a small but diverse army, with virtually no base management.
Starcraft 2 focuses more on controlling the entire map and countering the oponents' army composition.