I repeat myself from yesterday, with a minor twist: Battle: Los Angeles is more enjoyable if you watch it as a war movie than as science fiction. It borrows relentlessly from ID4 and Aliens, the former in plot and the latter in that it focuses exclusively on one platoon of US Marines as they go into evacuated Santa Monica to rescue civilians, then blow up a lot of alien stuff.
There are only two personal stories, really - the staff sergeant got the lieutenant's brother killed in Afghanistan (ooh, tension!); and a kid's dad dies - an incident that provides some out-of-place sentimentality and a chance for Aaron Eckhart as the staff sergeant to go all Marines Never Quit!! on us. They could've left that out.
We barely get to know the aliens. There is some hideous nonsense about them wanting our water (ocean levels have decreased several inches because they're using our water for fuel - what??!) but I'll just ignore that. The military stuff is handled believably to my completely untrained eye and - be thankful for the crumbs - there are two quite nice roles for women in this testosterone monsoon.
The movie is fun, in exactly the same way Cowboys and Aliens was fun. I think I would have hated this on the big screen, but the $5 blu-ray was just fine.