Lots of fun for rhythm fans, and may even convert non-believers. Easy to learn, hard to master.
Gitaroo Man is definitely one of my favorite games. It's one of the very few I never lend out, and I like it so much that, whenever I see one for sale, I have to resist the temptation to buy it again. It's that good.
The game involves a loser kid whose talking dog transforms him into Gitaroo Man, a superhero that defeats his enemies with the power of funk. It's that kind of quirkiness that is there for the hook, but the gameplay is more unique than most games of this kind.
Most of the rhythm genre involves just parroting back the game's moves, but you actually get the feeling of creating music here. The standard Parappa/Space Channel 5 Simon-says button presses are there, but only used when Gitaroo Man is in defensive mode. When attacking, you follow a twisting bar on-screen with your Control Stick, and play the Gitaroo (more fun than it sounds). Whether you do this correctly or not, not only affects your victory, but the sound of the music you're producing, and I found myself replaying the same levels frequently to produce a perfect melody.
The enemy will alter his own song if you're doing poorly, so there are technically several different versions of each tune depending on your performance. And after you finish the game once, there are harder versions of each song available with more individual notes and less room for mistakes.
As you might expect, the music in the game is almost universally great, and is in many different genres: Rock, J-pop, Heavy Metal, Acoustic, Surf, Blues...there's even a level where the Gitaroo sounds like a theramin, that thing they use for spooky sounds in 50's sci-fi.
This game has a learning curve, and not only when it comes to following the Phrase Bar. It'll probably take a little while for your hands to get used to it -- I had a terrible cramp in my right thumb after a day or two of play. It's not really an isolated incident either, as I've heard other reviewers make the same statement. It doesn't happen to me anymore, though.
Also, although the graphics are fun and the characters are cool, they could be a little cleaner. Some characters look a little jagged around the edges, but if you're paying attention to the Phrase Bar like you should be, you probably won't notice it all that much.
Basically, any cons I have are minor. All in all, a great game, and definitely a must-have for rhythm fans.