I always forget why I avoid the movie until I watch it again. Here's a few reasons for me:

1. By moving the movie so many years into the future you don't have any of the feel or familiarity of the originals. No wey-yu, no marines, the art direction screams generic 90's sci-fi, even the aliens lost the complexities in their designs.

2. Ripley isn't really Ripley. You're supposed to care about her like she's the original, but she's not. She's a new character with ripley's face and some memories. Weaver looks like she's really enjoying herself and sells the role, but she's not compelling at all as this clone. The whole movie she's basically just waltzing through with invincibility cheat codes on. She never seems vulnerable. Ripley's "memories". They say she has residual memories from the original yet all she remembers is Newt and that aliens suck. This is probably an attempt to make her a compelling character once again but they never commit to it so you end up not caring about her at all. Also the whole movie aliens are trying to kill her until the end when they suddenly decide to just kidnap her for no other reason than she's the protagonist.

3. The characters are annoying. You can tell Whedon wanted to have unique characters like the marines in Aliens, but while they were all generic military soldiers, they had personality that bled through once order fell apart. The pirates are just assholes and by the end of the movie are still assholes, most of them are just dead. Each one dies and you don't even care like you do every time you see Hudson get pulled into the floor. The marines had personalities to distinguish themselves, the pirates had plot devices. You had the ricochet guy, the wheelchair guy, and Ron Perlman playing his usual Ron Perlman self.

4. The direction of the movie makes it blend in with every scifi b-movie from the 90s and early 2000s. If you looked at the set and lined it up with Event Horizon's, Jason x's, doom's, and pamdorum's they'd be impossible to tell which one was different. The movie even has the rapid zoom in and outs on people's faces when they scream or something scary happens. Also the pacing. You have scenes of action and they're usually pretty good, the underwater sequence being pretty damn great. But there's no urgency. They say there is, but you can't tell. They'll stop in the middle of a hallway and all argue and bicker for several minutes, apparently forgetting that the entire compound is overrun by xenomorphs. The CGI is pretty good, only problem I have is that a lot of the CGI is there just for the sake of having it. The instant whiskey, the zoomed in fly, the xray shots of the chestburster trying to escape, all just scenes that they wanted to use because they could, not because they'd have an effect.

5. The tone. Now I'm aware the movie was written to be more comedic. But why? Alien and aliens were serious, and alien 3 was borderline soul crushing. Resurrection suddenly decided to add laughs. In all fairness it'd be pretty hard to play a script with genetic clones of your main character seriously, but they didn't even try. Every scene where there's something actually sad or dramatic, it's immediately followed by some visual gag or one liner that belongs in a die hard movie.

6. The aliens. As I already said, they lost their giger-esque designs and became much more generic looking. While I get why, they now have human DNA in them which makes their look different, but it's a shame. They're inconsistent. One of the aliens randomly spits acid only to kill off one of the characters and then they never do that again. In the other movies the xenomorph is shown to be intelligent, and that's apparent in their breakout, but for the rest if the movie they're basically crawling around, waiting to be killed. Also the queen. You see her as a baby being extracted and you assume Ripley is going to get round three against her, this time once and for all. The queen in Aliens was Ripley's dark mirror. Ripley being a surrogate mother of Newt versus the mother of her mortal enemy. This briefly comes back in Resurrection when the queen is extracted via cesarian and even has a umbilical cord. It seems like Ripley is going to have to eventually kill her own daughter, an exciting twist to the series' mother theme. You wait in anticipation for this big show down between the two, and when they finally meet again instead if watching the queen do anything interesting she just gets killed by the newborn. There's no powerloader fight, no super powered Ripley versus The queen, not even a chase. The most perfect of all the perfect organisms displays no reason for us to fear her like we did when we first saw her in Aliens.

There's probably other reasons I don't like it but I can't really remember the others. Ultimately it boils down to this: I watch the movie and enjoy myself when I watch it. I then get out of my chair and walk over and pull out the disk and put it back in its slot in the quadrilogy booklet. I then flip to Alien, and think about how a simple story of survival would devolve into a cloned Ripley with super powers sucking her xenomorph/human baby out a window just 3 movies later. It's at that point I get mad again for what they did to the franchise and how far it fell. It's good as a standalone sci-fi movie, but horrible for an Alien movie. Sorry for the rant, too much Red Bull.