Excellent movie.
I can see how people would draw parallels with Species at a glance, but definitely not the same movie. Dren is a much more "Frankenstein's monster" type of sympathetic being, while Sil basically turns into your run of the mill creature on the loose after pupating on the train. Dren wanted to be loved...Sil wanted to be bred.
It was interesting how the more "human" Dren became, the less "human" the scientists' turned out.