Well, both series are kinda dead now...unfortunately. I mean, they're not my sort of game, but in an industry where innovation is often confined to Nintendo and isn't always done particularly well, simplified and fairly accessible guitar-based gameplay is a nice thing. It's unfortunate that they don't seem to have a place on the current generation of consoles...or that there isn't any appetite to make them, anyway. I'm sure they'd sell very well if they did, and the DLC songs would no doubt prove to be extremely lucrative...although perhaps not, with the licensing issues.
I'll stick with Hatsune Miku and Theatrhythm though I think. xD