I'm pretty attached to Taiko because it's the first rhythm game I've been introduced to,
but honestly at this point it's probably Pop'n Music.
Though I can't really decide,the games I've played before (Aside from the two I've mentioned there's Ouendan+EBA,Jubeat,Reflec Beat,
Beatmania IIDX,Sound Voltex,Groove Coaster Zero,Cytus,Deemo and Dynamix)
are all pretty good in their own ways.
but honestly at this point it's probably Pop'n Music.
Though I can't really decide,the games I've played before (Aside from the two I've mentioned there's Ouendan+EBA,Jubeat,Reflec Beat,
Beatmania IIDX,Sound Voltex,Groove Coaster Zero,Cytus,Deemo and Dynamix)
are all pretty good in their own ways.