Like, it used to be one of the biggest franchises. Fucking everyone had some of those games. You couldn't go to a house without seeing a plastic guitar. It was a fun little game that encouraged hanging out together and you even got to listen to songs you like. Then it just kinda died overnight. How did they do that?
Do they have resell value?
Depends on the model. Older 360 controllers (the white ones in particular) are still considered solid choices, and Wii guitars have become the new meta after everyone discovered the RaphNET adapter. After that it gets kinda muddy on if the guitar is considered good or just passable.
Though if you're not doing Acai, Darkly, or FrostedGH level gameplay your options are much, much wider. The "good guitar" charts are mainly for when you get to the level of learning complex tapping patterns, where a slow polling rate for inputs can eat or overlap your button presses and drop combos.