I re-watched the film last night, and while I do admit that there are some subplots which could've been done away with, I still enjoy watching the film and just don't see what everyone else does. I tried to watch the film with an objective eye and I just don't see what the big stink about it is. Never the less, there are somethings which were pointless and could've been done away with, not to mention some things could've been improved.
But here is what I found that could've been omitted or improved upon.
1) Ricky and Jesse Subplot: This is something which could've been done entirely away. Really, this subplot was something which I don't think should've been in the film. The pool scene was also something that could've been omitted.
2) PredAlien Design: This is something which I believe could've been improved upon. We've only seen a few PredAlien designs, stemming from the comics and the games-- each having different appearance from how such a creature should be depicted. However I think the PredAlien could've looked better with more a bio-mechanoid appearance and less of a Predator appearance. Also, the dreadlocks could've been omitted as well and I would've liked to seen a more Predator visage around the mouth area that closes around the entire maw area.
3) Alien Design: I will conceed that these Aliens are not the best we've gotten. As a matter of fact, the Aliens from the first Alien vs Predator looked so much more better than the ones in Requiem. They looked really disproportionate in so many ways and their heads were too thin and too shrunken down and their necks were too plump and flesh appearing. Really, they could've done better with these Aliens.
4) PredAlien Reproduction: Pointless. Absolutely pointless and done mostly for shock factor. Really, I think this could've been entirely omitted and reproduction should've been entirely done differently. Egg-morphing would've been infinitely better than the regurgitation process.
5) Alien Gestation and Growth: Something entirely unresolved since the first AvP. This could've been improved upon by actually going with the twenty four hour gestation process and growth rate.
6) One Predator: I really think that a group of Predators would've been better suited to handle the Alien infestation. Why just send one Predator? I know Wolf was supposed to be this experienced veteran but a little back up wouldn't have hurt to have incase things get too difficult as far as hunting Aliens goes.
So far that's what I found, but aside from these six reasons which make the film flawed, I still enjoy watching this movie and really don't see the need to hop on the hate bandwagon.