It was okay, but the first one was way better.
I did like the scenes showing how alien technology was fused with human technology, and the remnants of the alien ships lying around. What I didn't like is that they rebuilt most of the cities, AND landmarks, in 20 years. 1 WTC alone took 13 years to decide, design and build. I also didn't like that they changed the alien's goals. In the first movie, they clearly sent millions of invasion troops. Why would they do that if they only wanted to drill to the core?
Clearly, the characters of Liam Hemsworth & Jesse Usher were meant to be Steven Hiller and Dylan Hiller. Dylan is together with the president's daughter. Steve flies Levinson to the moon to investigate the sphere, and they barely escape the mothership. The Aliens kill Steve's wife, then Dylan makes that "you have to lead us" speech, then later Steven pisses on the floor in the mothership.
The movie was pretty unstructured, and it felt like they cut out 10-20 minutes. There is one thing I remember where the accountant guy asks "What are those blue lights?" on the mothership and it leads to nowhere. I think they caused the gravity to turn around, but that's only a guess.
There was not a single original scene in this film. I get the feeling that VFX Studios pitch stories now, saying "show crumbling buildings here, crumbling earth there, and waves flooding everything, we did that already, it's cheaper for you." I also wished they had come up with a better idea than to borrow the alien queen/bee hive idea yet again.
Levinson's father Julius, as well as the Kids, were completely pointless in this film. Which is ironic since he even claims in this film how his idea saved the world in the first film. In the first movie, every character had a valid purpose. Some where introduced as likable, to cause an emotional Impact when they're killed off. Some move the plot forward, like Julius when he brings up Area 51 or triggers the virus idea.
I didn't feel any emotional impact in this film. When the cities were destroyed in ID4, and the short sequence of silence followed, I had a lump in my throat, as well as the characters. In this movie, probably another half a billion people die in 20 minutes and no one cares.
To top the emotional impact of the destruction in the first film, as well as the feeling of devastation, I would have destroyed Earth in the first 30 minutes, and let the refugees, led by Levinson and Presiden Lonestar, find the sphere aliens and prepare the resistance/vengeance.
And a BIG issue: David Arnold not scoring this film. Seriously, how can you follow his amazing original soundtrack with such a bland, generic one? Why did they only quote one single theme and not re-use all of them, even though the setting and characters are the same? When the end credits play all the themes that are not even used in the film itself, it's really getting ridiculous. I wonder why the importance of film music has been so completely ignored in this one.
Some minor stylistic issues. I would have kept the flashes that appear in the first act of ID4, as well as the intro credits. That was part of what made ID4 different.
The sound design was extremely bland compared to the first one, especially the alien fighters and alien laser blasts.