D-Pad Hero is a GH clone for the NES (ROM), but can also be played on the DS if you have a Homebrew card and NesterDS.
The game uses the A and B buttons in conjunction with the D-Pad (i.e. hold down a button and press the direction). Truth be told, it's pretty hard. Maybe if I played it on a controlled I'd fare better, but even then it's hard to keep track of all the falling notes and what not. The thing is, it's not like you can start on an easier and work your way up. There's no indication difficulty wise whether you're going to get brutally raped, or only kinda raped. It's something you need to practice at I guess, but there are some parts that just seem impossible.
There are 4 songs all rendered in 8-bit:
"Sweet Child O' Mine" by Guns N' Roses
"Harder Better Faster Stronger" by Daft Punk
"The Swing Of Things" by a-ha
"The Way You Make Me Feel" by Michael Jackson
BOTTOM LINE: For what it is, an experiment to make GH on the NES, it's good. I'd obviously love more songs, and difficulty levels, but as it stands, it's worth a download.
P.S. Even though I mentioned that it's too hard, I'd be curious to play Rush's "Spirit Of The Radio"