I approve of this thread.
Guitar Hero is one of those games that makes you really happy to be a gamer. It's a rhythm game that's actually cool. Not only is it easy to pick up and play (at least at first), but it's hard to put down - even for non-gamers.
My dad, for instance. Seventy years old, and he was grinning from ear to ear the first time he saw it. My girlfriend's the same - she's practically addicted.
What I love about the game is its deep song selection and sensible learning curve. Not only are there 30 great, classic guitar tracks, but there's also several indy tracks to keep you occupied for hours on end. There's just something about jamming to faves like ZZ Top's "Sharp Dressed Man," Judas Priest's "You Got Another Thing Comin'," Franz Ferdinan's "Take Me Out," Megadeth's "Symphony of Destruction," and more by the likes of Deep Purple, Joan Jett, Helmet, Zakk Wylde, The Red-Hot Chili Peppers, and even Stevie Ray Vaughn.
The learning curve is steadily challenging and thoroughly satisfying. You'll fight your way through Medium, be flabbergasted by the first few songs on Hard, but then something clicks and you start making progress again. By the time you go back to Medium (as warmup at the start of a new play session), you'll be amazed at how "slow" it is and at how much your skills have improved.
The guitar peripherals are solid and incredibly fun to use. Like my girlfriend says, they make her feel like a real rock guitar player.
Add to all this a top-notch presentation that's filled with fun and personality, and you have a game that's number one in my book - with a bullet. Guitar Hero is pure gold.
Rock on!