Apparently playing a toy miniguitar with no strings is awesome.

GHII is the followup to the vastly popular Guitar Hero. I haven't played the original yet, but I did play GHIII before GHII. II and III are very comparable, but III has a tiny edge for me; I like the song selection on GHIII better. At least,

there are more songs I really like on GHIII, but GHIII has some truly awful choises as well, whereas GHII has no absolutely terrible songs. Ofcourse this is just a matter of music taste, if you find yourself wondering which of the two to get, just look up some of the song lists to decide what appeals to you most. 

Bear in mind though that 95% of GHII's songs are covers. These covers are decent, but sometimes it feels like they picked the wrong type of voice for some songs. Some of the covers are actually for the better though, I liked the GHII Freebird more than the original version. GHIII on the other hand has some covers, but a fair amount the of the songs are either master tracks, or rerecordings by the original artists. This is slightly more fun IMO. 

GHIII is known for it's rather hard difficulty on Hard and Expert. GHII is probably somewhat easier, but this also depends on which of the two you played first. GHIII's difficulty kept me coming back for a good challenge though, while I grew tired somewhat faster from GHII.

GHII is a really fun game, addicting and with some great songs to play. I really recommend it to anyone who feels like some mindless fun.