I don't know how many people are interested in shoot-em-ups (shmups), but anyone who is and has a DS should seriously check out Ketsui DS. It's Japanese only, but the gameplay doesn't require any knowledge of the language, and DS games aren't region locked so you can import it.
Or just get the .NDS and stick it on an R4
Gameplay is expectedly difficult, but it has quite a nice difficulty curve to start with, and with each game over you get more lives the next time, so eventually you can have all the modes completed and work on score-attack
Trailers:
http://www.youtube.com/watch?v=dOaTEuRfOlU
http://www.youtube.com/watch?v=Yhfq53if8hE