It is not as cool to recommend it since Elite Beat Agents is out in the US now, but the Japanese original is a lot better IMO. And it is half as big at 512k. But I keep both on my g6 anyway.
There are a dozen threads like this already. The topic pops up every few weeks. Use the search function, there is a thread like this where I linked all the other threads like this I could find.
Wow, the same misspelling three times in one thread! It should be Ouendan, not Quendan.
But yeah, that's like the best JP game available right now, at least until Gyakuten Saiban 4 comes out, which I wouldn't even recommend unless you speak Japanese, due to a heavy focus on story and dialogue.