What a shame to use such stunning technology for such a derivative, hohum, politically-driven script. Based on an amalgum of old SF plots, it tries to make the earthlings greedy polluters with no morals. I resent painting all of us like that and don't think the "marines" would have so one-dimensional. Why didn't the creatures just drop rocks down on the helocopter blades? In one scene,the hero seemingly jumps off a cliff where you can't even see bottom and falls forever. Then he looks up about 20 feet to look back at the creature at the top of the cliff.
My only recommendation would be to totally suspend belief and do not thinkj as you are awed by the 3d effects. Withoug 3D this would be a loser.