I've been a dedicated GH fan since the series started and even with the release of rock band before GH could release their version of a full band with World Tour, I still remained faithful due to the brilliant song list.
Unfortunately looking down the list of songs on GH5, I saw about 10 songs I recognised and about 3 I liked. Guitar Hero has quickly became Indie Hero. Sorry, but how hard is 'sex on fire' and 'never miss a beat' to play? Yeah fun songs to sing but I can't recommend the game for MY PERSONAL song preference.
Due to the song list, I'd only give it 3 stars, really it is a good game still, good features as always and graphics are improving all the time.
If your going to get it, I think I'd check out the FULL song list first.
If your after a game full of challenging solos, try Greatest Hits, the songs (I believe) are a lot harder to play on Greatest Hits than they are on the previous versions.
I remember Through the Fire and Flames being unchallenging once mastered once on GH3 but it was more difficult on GH:GH.
Also Beast and the Harlot on drums is very fun indeed!