Can I make my GH2 guitars work on my PS3 with the PS2 game, using a standard PS2-to-USB adapter for PC?

May be...

If it works for GH2, would it work for the PS2 GH3, and also on PS2 Rock Band?

Yes the Guitar Hero II guitars work with Guitar Hero I fully and Guitar Hero II mostly on the PS3. It won't work with Guitar Hero II however.



In Guitar Hero II the strum bar might be reversed and the whammy bar will most likely not work, and also there WILL be a bad amount of input lag which cannot be callibrated (so the notes you strum will take a little longer to get to the system and it will be a little off sync with the game).



This is the adapter I use (it works 100% with all games that use the DualShock, for both PS3 and PC):



http://www.ztnetstore.com/product_info.p...



Hope that helps! :)



Also one more thing: It will not work with Rock Band or Guitar Hero III.

yes it does