One of the most underestimated game in the beginning and has become quiet popular, even I got the power and influence of Guitar Hero wrong, mainly due to some of the music tracks, which then became very catchy, which may explain its popularity.
For those who don't understand about the whole Guitar Hero phenomenon, in clear and short, it is a guitar game which players match button pressing with stumming and it is a lot more easier than it seems. If you press the wrong button during a strum, there is an annoying *kink* (I would try to use another word, but apparently, it is quite impossible) sounds and the guitar notes won't play if you miss your strum.
Its raise to fame isn't because of the guitar, or because it is a guitar game, just check your local arcades for a game called GuitarMania, but it lies in the pop culture of the music tracks within the game. Some songs which people may not associate with, some people do and there are some which are just down right damn good. These tracks range from 70's to the modern ones, from the Rolling Stones to Bloc Party and The Killers. You may call some of the tracks to be off-key and down right unpopular, but try playing the game and attempt to clear the song. It is in the game for a reason, not because of difficulty, but because of the movements which must be pulled off in order to accomplish a 5-star for the song. one major example of this is DragonForce's Through The Fire & Flame, where it is not only rampantly difficult in expert, but those new to the game and tries to attempt it on easy, will have difficulties playing the track, I even have problems if I try to do it when I've been playing the game on medium, it down right made me keep focus, and damn, that is one brilliant song too!
Though, some of the negatives would be the catchy nature of the game and how much distraction it causes to you and how much of a headache it can provide when you are working and just want to 5-star bloodrape a track or a boss battle, which was introduced in Guitar Hero 3. Other than that, there's the cost of downloading new tracks, roughly $USD2 per track, some of the tracks in Guitar Hero 3 isn't that good; but only few are just top notch; the guitars from Guitar Hero 3 doesn't work in Rock Band, which is a fusion of guitar, bass, drums and vocals in famous track titles; rampant difficulty in the new version and advertising within the game.
On the mention of Rock Band, it isn't by the same "makers" but the same "co"-maker of the Guitar Hero series before Guitar Hero 3, where so many of the tracks were beyond brilliant, over 50% of the tracks were down right great and Guitar Hero 3 has about 20-40% good tracks titles there. Both makers from Guitar Hero 1 & 2 are now competitors and with the release of Rock Band in the states (damn you greedy tarts for pushing the release date of the Aussie version of the Rock Band back for months on end!), the phenomenon of the casual colour matching games is truly a new era in home entertainment where the previous technological phenomenon was the eye-toy (don't correct me about the Wii as the Wii came right after the Guitar Hero and I know about the popularity of the Wii as I had problems looking for one in the stores, explains the raise in popularity of the PS3...) and even though it wasn't ported to the Xbox, it still was a popular focal point of the Playstation 2.
A few months ago, the same developers of Guitar Hero has Trademarked the name "DJ Hero", so we may be expecting a new branch of casual colour matching games, main problem they may face is the fact that there is something similar of that nature in the game arcades already, decked out with a scratch kit and 5 buttons; 3 on the bottom row and 2 on the top. But there may be a major change from this approach, we'll just have to see.
Though possible titles which we may see may be Drum Hero, for those Drum addicts (all in if it comes out!) and Piano Hero, for those who loves their classical music.