@Sie your situation reminds me that I did not complete my Master's Degree, in part due to the research that was involved :P Can't write shit when your paper's going to be reviewed by a panel of PhD's... and you can't write shit when your text is going to be reviewed by the Internet :S
I think PaRappa is technically the first. So I'll say PaRappa started off the genre, Beatmania refined the genre with custom controls, Freq./Amplitude refined some existing concepts, and TH popularized it. Sound fair? Lol.