The Taiko drum game is actually pretty fun to play. My wife and I played it a bunch on our last trip to Japan. There was some weird feature at the end of the games, where you could snap a photo of the barcode on the screen with your cell phone. I think it was some sort of save feature, but the screen came and went to quickly for me to understand.
We also played this 'whack a mole' style game, where you hit the screen with a soft hammer to banish ghosts. It was fun, but it had a lot of written dialogue in the game play and I don't read japanese very quickly.
We didn't spend a lot of time at the arcades last time because we were so busy seeing all the sights. But our next vacation there in February is more low-key and I think we'll get more time to play games. I'm planning to snap some photos of the different cabinets for inspiration on building another arcade machine. It's research, see?