Although I really enjoy the environment destruction in Battlefield: Bad Company, it is fairly scripted. You can’t dig too deep into the ground, you can’t completely destroy any of the buildings and when you shoot an explosive at a wall it always breaks a hole a certain size in a certain position.
Red Faction: Guerilla is supposed to come out in January and it boasts proper destruction – you can take down whole buildings, and it uses real structural physics.
The only down side (for me) is that the surface of Mars isn’t as much fun to play on as Earth.
Apparently there’s a beta of Red Faction: Guerilla, but unfortunately I’m not in it 
