The first AvP movie had a great concept that works in the lore of the comics. The history between Yautja and Xenomorphs is long, and that they chose Earth with primitive beings that could be used as hosts and food for Xenomorphs and make it a hunting ground is pretty cool really. The biggest issue is a cast that just isn't very strong, plus they had to make it PG13 so the kids that know the comics and games can watch and well, their you go.
Requim was, as said, just awfull. It was nice seeing a PredAlien on screen, and the level of gore was what one might expect from a Predator movie, compared to AvP. But if that's all you're going to base your movie on, you're already loosing.
Predators and The Predator..... I both enjoyed them for what they are. Predators actually a lot more than The Predator. But for a mindless popcorn flick with a few beers, The Predator is still a lot more entertaining than Requim
The original Dark Horse 6-part AVP comic story would have made a better movie, but that's water under the bridge.
The Predator- it almost seemed like a spoof at times, but I had forgotten how funny a Shane Black screenplay could be (Think Lethal Weapon, for starters), and they policed up the perfect cast to play a bunch of psych-ward commandos. At times I was laughing my ass off, so hard my wife had to ask me what the hell I was watching and how it could be so funny. Although it is fatally flawed as a Predator movie, I thoroughly enjoyed it.