There are two ways to see this film and rate it.
1: As a movie that turned out to be much worse than it intended to be. In which case it's obvious that an actor like Jon Voight would overact to try and make it look like it was intended to be "bad". The special f/x, intended or not, are done with computer animation and are, in that category, the worst i've seen yet. A snake that moves like a cartoon. If it was the movieproducers' intention to make a "bad" movie, they would have done better to use the old fashioned special f/x, with a rubber prop.
2:As a movie that was, indeed, intended to be a b-movie. However, since the director Luis Llosa previously only made "serious" action movies like "the Specialist" and "Sniper", i have to seriously doubt it was his intension to make a "tongue-in-cheek" movie. If it WAS his intention, he nearly succeeded in making a fun "bad" movie.
Personally, there were only two things in this movie i enjoyed: The voluptuous Jennifer Lopez, and the magnificently "bad" performance of Jon Voight, who with just the facial expressions brings a smile to your face.