Guitar Hero II 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.
What I loved about the first game was its' deep song selection and sensible learning curve. Not only are there thirty 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. I've heard it will be the same with the tracks in the 2nd game also - particularly Megadeath's "Hanger 18".
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 warm-up 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. 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 II is pure gold.