Keep in mind, that Cave is asking Japanese users to send in Japanese emails for which games they want on Japanese Xbox 360s. But! Cave shmups can't be that hard to localize, and we're fairly confident that Cave would be interested in knowing if players outside Japan are interested in having Cave shooters on consoles outside Japan.
Here's the email address: email@example.com
We imagine emails in English are okay, too!
Cave Blog [Official Site]