Yeah, there are a lot of shmups on the 360, especially in Japan. Maybe it's easier for developers to port the arcade games to the 360? You can actually find quite a few that have western releases as well such as Deathsmiles, or the various Raiden games, etc. Just search around. Sometimes the games released are region-free such as Espgaluda 2. If you check somewhere like Play-asia.com, then they usually list if game is region-free or only playable in certain regions, it's pretty helpful.
The 360 is definitely the console of choice if you are a shmup fan. I have a JP 360 (as I am in Japan), so I have no problems getting the games (only finding the time to play them all!)
starcraft: "I and every PS3 fanboy alive are waiting for Versus more than FFXIII.
Me since the games were revealed, the fanboys since E3." 
Skeeuk: "playstation 3 is the ultimate in gaming acceleration"
