This type of statement would normally be premature for a game new to the market, however the Guitar Hero series by Red Octane has been around for quite some time. Originally designed and released for the PS2, Guitar Hero was released in November of 2005, and was followed by a sequel in Guitar Hero II a year later, almost to the day. Based on the success of the series and the success of Microsoft's XBox 360, a port over was inevitable and, quite frankly, overdue.
I would not blame anyone reading this for being more than a little concerned with that last statement. Yes, I said this is a port knowing full well that ports are usually simply vehicles for developers to cash in on another company's technology. Simply tweak the game and viola, another segment to drive revenue. Fortunately, Red Octane and developer Harmonix did the game and the console justice, producing a updated game, better than it's predecessor in every way - and that's a very, VERY good thing.
The Graphics
The weakest part of the game is the graphics. That is not to say they are bad...far from it. The game is now presented in glorious high definition, and the colors and textures are exceptional. Fantastic lighting effects make you truly feel like you are a rockstar on a stage in some seedy bar to holding your own out in a grand amphitheater. The crowd reacts according to your play, chanting and moshing at one point, and then swaying like a tree in a breeze while holding lighters aloft with your next song.
The Sounds
From there it just gets better. With the new hardware comes full 5.1 surround sound matching the visuals of the stage with the sound. At the start of a song, you can hear people start to cheer you on, or jeer at your attempts to play. As you get into the song, applause will start from sections, and build into a full on roar provided you can give them what they want - a rockstar performance.
The Gameplay
Finally, the crem de la crem, the gameplay. Guitar Hero II is a rythm game using a unique controller fashioned in the likeness of a Gibson X-Plorer guitar. The controller consists of a series of fret buttons on the neck which you depress to play the "string", a strum bar where you would normally pick the strings, and a functional whammy bar. The controller acts intuitively even for those who, like myself, never have picked up a real guitar in their lives. You find yourself naming a band, and entering a career mode as the lead guitar player of an up-and-coming band. With four difficulty levels and over 70 songs to be played, there is more than enough variety for the player new to the series, or someone who is a seasoned veteran of the PS2 version.
Downloadable Content (DLC)?
Last but not least, if there was ever a game made for downloadable content, Guitar Hero II is it. Word on the street is there will be content available within the first week of release, including the soundtrack of the original game. Pricing has yet to be released, but it wouldn't be a long reach to assume a pricing scheme similar to other online music services (e.g. iTunes). In addition to new songs, it stands to reason we could see new players, new guitars, and new outfits as well. All in all, the longevity of this game is shaping up to be as extreme as the gameplay.
In conclusion, if you are interested in a fresh, unique, and addictive game that will suck you in and make you feel like you're a rockstar, do yourself a favor and buy this game. While the pricetag of the game and controller are on the steep side at $89.99 USD, the amount of sheer "fun" in the box makes it a small price to pay.
Final rating: two rockin' 
