My friend just saw this and he said he was outraged at how much of a rip-off(s) it was. He said they stole stuff from no less than "like 9 movies and 3 TV shows" and when asked, "off the top of my head every Mad Max movie, Gladiator, Lord Of The Rings several times, Resident Evil, 28 Weeks Later, The Warriors, Escape From New York, etc" and further stressed that they specifically ripped off LOTR "like 5 times", and also shamelessly from stuff like Prison Break.
He also said, however, that it made for a pretty entertaining experience, like sort of a "Greatest Hits" movie, which is neat.
The writer has openly excused himself by saying he wanted to do a bunch of homages to some of his favourite films. What I think he should have done is hyped it this way by advertising it as an edgy new film experiment: a "serious" film-compilation parody as opposed to the comedix ones done by the Scary Movie people.
In fact, that's an idea that may have something to it...