As for me there are several japanese rock and pop bands/artists that I like:

The Pillows
Bump of Chicken
Do as Infinity
Mucc
HYDE
L'arc~en~Ciel

Loudness - Soldier of Fortune song in particular

Gackt is pretty good

Well, when you're Japanese you tend to like a lot of Japanese bands.

Nice to see people that like LOUDNESS, although I haven't seen them live in the longest time. Been spending more time trying to get tickets to shows for acts like Versailles, Moi dix Mois, and BUCK-TICK.

i love BUCK-TICK. they were one of the first bands I got into. I also like:
La'cryma Christi (they disbanded this year =/)
Kagerou (disbanded now too~)
Schwarz Stein (good techno/trance music, but they disbanded too lol)
GO!GO!7188 (one of the few, very very few bands with chicks actually playing instruments well)
Yellow Machineguns Malice Mizer
Charcoal Filter Tsubaki
D (ish okay~) Kagrra
Love Psychedelico

i've heard of newer j-rock bands. they all seem to be mimicking each other =/ and i've heard a lot of bands come out with TERRIBLE singers. i think its an epidemic, but luckily its mostly in the visual kei genre~ lol

I've been rather stubborn and tend to listen to my main 3 (mainly because I'm picky and have been spoiled by their music lol)

My main 3 are:

1. the pillows (my favorite band whom I would compare to The Beatles any day of the week)
2. ZEPPET STORE (greatest unknown J-Rock band EVER, I'd liken them to a Japanese Radiohead except all their albums are either another The Bends or OK Computer in terms of how the music sounds)
3. L'Arc~en~Ciel (Definitely a very creative group and also an extremely talented ensemble of musicians, ken and tetsu are definitely a great guitar/bass team that I would liken to Alex Lifeson and Geddy Lee)

And pretty much I enjoy all 3 groups side bands (especially S.O.A.P.)

Other bands I'm interested in and listen to: AKG, ART-SCHOOL, Supercar, THE ALFEE, hide, Kaela Kimura, Noodles, wino, The Babystars, X Japan, Zi:Kill, Luna Sea, Buck Tick

The Pillows
Asian Kung-Fu Gen (Aji-Kun)
Maximum the Hormone

Those are my top three favorite.

A friend of mine is in love with this one Japanese song, I can't think of the name but I will find out and post it here.

He tried to request it for Guitar Hero (for some diversity) because it has some sick guitar in it.

I love the Japanese rock music.
I can't understand the words but lets face the facts, it's all about the same stuff anyway.
It sounds really cool though when you do learn the words and people say, "hey! that is Japanese isn't it?"

I like the Latin Rock music too but I can understand that because I speak Spanish.

I really think that the developers should add an international mix to the selections because Rock music is not exclusively English language.
Just my opinion.

Yeah there are quite a few Japanese bands that are honestly just better bands PERIOD than some of the crap that is here in America so I think it's about time some of these bands finally got recognized.

I think L'Arc~en~Ciel would be a perfect fit for Rock Band since they're a very significant group that has countless fans in both Japan and a strong following in America (they're even starting to release L'Arc's albums on iTunes USA), plus their songs generally require a bit of technical proficiency to play (even the ever so crappy and overrated Ready Steady Go) on all sides of the equation.