Now let's get to the fun and meaty part...
First, though, your writing style is good; you write like you are having fun with this, and that translates well to the reader.
What does not translate well, though, is your ratings.
GORE: 5 out of 5. Exploding bodies galore.
BOOBS: 0 out of 5. No naked boobies to be seen.
BUBBLING GREEN SLIME: 1 out of 5. I'm being generous with this, for the greenish-beige acid the eggs spray.
TOTAL SCORE: 6 out of 15.
I still don't know what you thought of the movie other than...
Today's pus-laden boil of mediocrity is "Alien Contamination"
6 out of 15 doesn't jive with 'mediocre', nor does totaling the amount of gore, nudity, and...uh...green slime for a composite rating give any satisfaction to the reader.
Keep in mind that gore, boobs, and...uh...green slime are fine things to rate in a movie, and add a bit of fun to the review, but having some kind of rating that cements what you really thought of the movie would add that much more to it.
I would recommend 'spoilers alert', or some other type of warning, that soon you are about to give away a good bit of the ending of the movie.
Though your outline of the film seems a little choppy...well...you didn't have much more than that in the movie with which to work anyway.
I enjoyed the film more than you did, but I don't find myself disagreeing with you too much either.
I'll rate your review at:
Gore - 0 (didn't see any)
Boobs - 0 (damn...didn't see any either)
Bubbling Green Slime - 0 (was really looking for it too)
Overall score 7-8/10 (really couldn't decide)
Overall you did a pretty good job.