Finally got around to seeing this movie. As others have said, it's not a great movie, but it's fun for what it is.
A few funny things struck me about the characters. Tsuchiya plays a biologist sent by the resort company to do...what exactly? I know Kubo's character is supposed to photograph the island to help the company promote their resort, but I don't think they ever explain what Dr. Miya is doing on the expedition.
I also love the convenience that Kudo just happens to glance out his window at the precise moment the Telios 7 crashes, and it just happens to crash land near the island he is later asked to photograph.
Sahara is great as Obata, though I found it amusing that upon being confronted about his stealing of the resort plans, he immediately admits he's a corporate spy and hands the documents back to Ms. Hoshino. I really don't see his motivation for doing so. He says something like "Our lives are more important than this." Gezora has attacked at this point in the movie, but Obata hasn't even seen the monster with his own eyes, and is skeptical that any monsters exist. I think it would have made more sense if he came clean about his agenda after narrowly escaping one of the monsters, or something like that.
Speaking of the monsters, I was a little confused if these are supposed to be monsters that already existed, but were possessed by the aliens, or if they were normal animals that were enlarged to become monsters, and they just happen to resemble monsters from the local folklore. Either way, they're a lot of fun to watch, especially during the ending battle. I love the moment in the the commentary track where the interviewer asks producer Fumio Tanaka if there was one alien that was hopping from body to body or if there were multiple aliens; Tanaka just laughs and says "I don't really know."
This movie reminds me a bit of Godzilla vs. the Sea Monster...four people get stranded on a south seas island, including a criminal who redeems himself by the end of the movie and both movies feature multiple monsters, including a giant crustacean.