Yeah, Jim, I think we've all been watching movies since we were kids, probably most of us that post here have that qualification.
But all you got from District 9 and Black Hawk Down is "D9/BHD != Earth invaded?" Not that I'm saying B:LA looks like a ground breaking movie or anything, but it doesn't really look like the same feel of ID4. It looks like an alien invasion movie from a different perspective we haven't really seen - that of a small unit leader, in this case a Marine SSG. It has a grittier feel than ID4 w/out any of the witty/comedic moments hopefully - ID4 really shouldn't be the Earth Invasion alien movie we compare to, it really wasn't that good.
District 9 was certainly nothing like ID4.
For Battle: LA, I liked just listening to the music from the trailer. Its good to return to the idea that aliens want to eat us and take our world, not be blue and beautiful while swinging from trees in a movie that was basically a Ferngully remake.