According to ESRB, this game contains: Suggestive Themes, Violence
Parents should be advised that the main theme of this game is shooting and slashing hordes (or 'hoards', if the back of the box is to be taken literally) of alien monsters. Sure, they're alien monsters, but if you don't want your child to be exposed to violence, this is a no-no. There are also some outfits for the female characters that are a bitrevealing, and are not suitable for young children (or anybody, if you don't want to catch a cold).
Fans of Dynasty Warriors might want to check this out as this game offers up fairly similar gameplay in a different setting. Gamers in general might want to give it a rental if they're intrigued, but it's fairly safe to give this one a miss.
Hearing-impaired gamers should be glad to know that they won't have to listen to the cheesy voiceovers and can just enjoy the competently done subtitles.