I felt that Species II was better than the original. It takes the same alien-sex-beast-on-the-loose idea as the first film, but gives it a T-style twist which works surprisingly well as the sci-fi/horror is mixed with an interesting military prespective. This sequel has a completely different feel to it than the original. While it has the same 'impending doom' idea, just twenty minutes in two alien children have been born - a feat that took Sil the entire movie in the first Species.
I found Natasha Henstridge's performance mesmerising as Eve. She manages to bring a whole new dimension to the film as the alien trapped within a large glass pen and manages to make you feel sorry for her (and I can honestly admit that as she escaped I was cheering). Both Marg Helgenberger and Michael Madsen returned for this sequel, and I found them enjoyable, although it would have been nicer if their characters could have been deepened.
The special effects are all spectacular, with the exception of the final showdown between male alien and the humans. At times [director] Medak seems unable to handle the more demanding effects, and so they come across as either extremely clumsy or fake-looking. But other than the final showdown the effects are top notch and as impressive as the original's.
Very different to the first movie, and yet very entertaining, Species II includes some spectacularly gruesome special effects and a great cast - it gets an enthusiastic thumb up!