I've gotta recommend my favorite bands Asian Kung Fu Generation and UVERworld.
Both have great songs with great lyrics.
The Brilliant Green is also very good.
For visual kei, I'd recommend Alice Nine, The gazettE and An Cafe.
also, I love Otsuka Ai. very cute and has some great songs.
I've come to really love Japanese music in the past few years and love finding new bands/artists to listen to. I absolutely LOVE Arashi. They are my biggest passion in music right now. GACKT, T.M.Revolution, SINCREA, and Utada Hikaru are also favorites. I've also recently discovered two stage actors, Watanabe Daisuke and Hamao Kyousuke, whose voices I love. These songs are among my favorites! And yes, my taste in music is quite varied. lol