SPOILERS: The ending was... um what the !@#$???

Guys, it was 2 alien races using earth as a battleground, the very last scene shows 2 completely different alien motherships battling each other above the earth.

I think the jist of the story was that the first aliens that came had put aliens in human form on the ground several years earlier to learn what humans were like, JCVD explains to the group that the aliens learned that mankind's governments had spent far more time making up plans and strategies about how to fight aliens and not many plans about how to communicate with them. The aliens then decided that humans were far more interested in conflict rather than diplomacy so they started attacking.

At the end of the movie fighter craft from a different alien race, a friendlier one (atleast we assume they may be friendly, they may have just been destroying the other race so they could then conquer us instead), you can see during the dogfights that the original alien fighters were blueish lit and had tentacles hanging down from them, the second race had fighter craft that looked more like fighter jets and had purple lights on them and fired purple lasers.