To me it was the throwing together of every sci-fi and horror movie into a blender and then pouring it out into a mold. In the near future a portal is discovered between Earth and Mars (Stargate). A base has been set up on Mars and a corporation is doing something up there. Something goes wrong and the Marines are called in to investigate (Aliens). There's lots of running around the base chasing whatever is up there. You never get a clear idea on just what the Hell was supposed to be going on on Mars. It turns out they find a missing chromosome pair from some sort of alien life and inject it into test subjects. It turns most into savage beasts/demons. I was never sure if one beast was responsible for transforming the other humans into beasts or if it was like a zombie movie in that once you're infected you can infect others. Yes, it turns into a zombie movie towards the end. There's also a climactic battle between The Rock and another marine which could have come from any kung fu or Matrix movie.
There is one segment when they turn the movie into a first-person shooter where the camera perspective is supposed to be that of the actor. It was actually pretty fun although one segment made no sense whatsoever unless it was meant to imply that you die and are revived just like in a video game. I had to MST3K a shot when they showed a dead researcher hanging from the rafters with a rat eating his face through the eye socket. I yelled out, "Oh my God! They killed Kenny!"
A few other things. In one scene I swear that one of the actors opens a window...ON MARS! WTF? Perhaps he was only opening shutters, but it sure looked like the shutters simply opened to the outside. Also, why is every sewer pipe in every horror movie like 8 feet in diameter?!? There were fewer than 100 researchers on Mars. Why is there always this extensive network of huge pipes?!? It's not like there's a lot of water on Mars that you need the drainage. And why is a nice shiny research facility connected with dark claustrophobic hallways? And why are some doors old skool while others are made of liquid metal? I bet someone thought that effect was cool and so they had to incorporate it in the movie somehow.
So in conclusion, it was worth the price of admission...$0. If you want a totally mindless movie and feel like parting with $9-$11 go see it.
A funny story from the show: As we were waiting for the movie to start a person in back of us asks Kitty if she was at the Longsford Homes open house last weekend. She hesitantly said "yes" and asked how he recognized her. It turns out he worked for Longsford and how could he forget the person walking around with the big dog dude. I kept my mouth shut and just enjoyed the moment.