I watched Battle: LA over the weekend, and I gotta say, I don't see where all the hate for this movie comes from. Maybe hate's a strong word, but I don't recall seeing a single positive review for it.
To summarize, it's the story of a Marine unit that's tasked with evacuating Los Angeles during an alien invasion. I don't want to get too spoilery in this, but I thought it was a pretty good movie. I can see how it might turn some people off though, because it doesn't really fit into any of the standard science fiction move genres, kind of like District 9. Not to say that the two movies are at all alike, other than neither of them really fits into the "blockbuster scifi explod-aganza".
The entire time I watched the movie, I was saying to myself, "these feel like real marines" they aren't supermen, they're not geniuses, they aren't unkillable. One of my favorite parts of the movie is during the first up close confrontation with an alien, a marine shoots it, and it falls back into a swimming pool. The other marines catch up to him, and the alien jumps back out, all of the marines fire at it until it goes back down, and Aaron Eckhart's character says: "Toss a grenade in the pool and let's get moving" in any other movie, they'd assume it was dead, or send someone in to make sure, and maybe take it into custody, but in this movie, they just want to get it dead, so they can continue with their mission.
This movie doesn't really have any deeper meanings, and really, slight spoiler, they don't completely fight off the invasion by the end. The marine's complete their mission, win a victory, return to base, and go back out again, that's the movie. There's some really stupid sounding stuff about why the aliens are invading, but it really just seems like it's supposition on someone's part, the aliens never communicate or talk, there's no big reveal, just people making guesses based on what they see.
So, if you want to follow a realistic group of marines through an alien invasion, this is the movie for you, if you want the next Independence Day, Avatar, or Distict 9, you might be a little disappointed.