TheKoreanGuy on 03 August 2013
I recommend the PSP games for the DJ max series. If you ever get a vita, you should consider getting Technika Tune although it is quite different from the PSP games. I still enjoy it just as much.
As others have said, Elite Beat Agents and Theatrhythm are easy choices. If you like Elite Beat Agents, you can download a PC game called Osu that plays very similarly. It's free and there's plenty of songs you can download with beatmaps created by the community.
