Edited to Add: Minor Spoilers Below
After the first AvP, I remember thinking that except for a couple of glitches it made for a pretty good Predator movie. The girl running around Antarctica in a tank top was ridiculous and I wish they hadn't bleeped The Line to get the PG-13 rating, but whatever. The Predators kicked ass and I enjoyed myself.
Requiem is just the opposite. In this one, the Predators get the shaft and the Aliens are the stars. It picks up right where the last one left off with the Alien-Predator hybrid attacking the ship and causing it to crash near a small town in Colorado. Across the galaxy, an alarm goes off and a single Predator rushes off to his space ship to... Well, I'm not really sure what he's trying to do.
Is he damage control? Does he just see a great hunting opportunity? Either way, I'm not really sure why he goes by himself. He certainly ends up needing the help, but then, he also shows that he's not the brightest Predator on the block. As soon as he's on Earth he gets snuck up on by a cop, and later on he's walking on a mesh catwalk and can't see the Alien hanging from the underside directly beneath him. Actually, it all kind of makes sense if he's sort of the Snapper Carr of the Predators, stuck on monitor duty when the alarm comes in and stupidly rushing off by himself with the deluded notion that he can handle it. But it doesn't make for a very cool Predator movie. They don't even say The Line. It's rated "R," so they could've, but they didn't. Very disappointing.
As an Alien movie though, it's pretty good. There's a great ensemble cast of small town citizens, including Michelle from 24 as a soldier who's just returned from Iraq. Michelle was one of three reasons I stuck with 24 as long as I did, so it was very cool watching her again, even if her military skills were put to use mostly as a driver and pilot rather than the machine-gun toting Alien-killer she should have been.
As in any good Alien movie, characters start getting face-hugged, bit, impaled, and burned by acid blood pretty quickly, leaving the rest of them to try to escape town alive. That's all I'll say about the plot, except that it's a great formula that works. The Alien movies are all best when they stick to it.
There are some huge plot holes that keep Requiem from being as good as Alien or Aliens, but it's a much more exciting movie than Alien 3 and doesn't meander off into complete stupidity like Alien Resurrection.
Three out of five chest bursts.