DJ Hero looks much harder. On screen you need to follow the crossfader line, detect the notes and scratch arrows, all of them on top of each others. On the control side you need to control the crossfader, turntable and buttons, and the buttons move with the turntable. Plus the effect knob, but IIRC, it isn't required, but it is important for scoring. But since the Guitar Hero robot doesn't use the star power, I think it can be overlooked.

Maybe an easier target would be BeatMania IIDX. It is actually a ridiculously hard game when played by a human, but the screen is very clean and you just have to press 7 button and move the turntable back and forth (or use the auto-scratch if that's a problem).