Guitar Hero 3, Guitar Hero Aerosmith: Can play Guitar with Remote. Nothing else.
Guitar Hero World Tour, Guitar Hero Metallica, Guitar Hero Smash Hits: Can not play any instrument, without having the actual instrument.
Rock Band 1, 2, Track Pack 1, 2, AC/DC etc etc: Can not play any instrument without having the actual instrument.
If you want to play guitar with just using the wiimote, all you have is GH3 and GH: Aerosmith.
If you have an USB microphone (any will do) you can play the vocals on all of the above mentioned games and nothing else. They do not support playing guitar using just the remote.