I played it for the first time yesterday, on a Playstation 2.
I would challenge anyone to top my sheer incompetence! I didn’t even beat the first song, “Slow Ride” by Foghat, on the easy setting.
I did manage to complete a couple of songs. Something by the Killers. Something by Poison. But wow, I suck.
Those things take a lot of practice. I’ve played similar games and there’s a curve - you suck for the longest time until suddenly you have a breakthrough. That is, if you decide to ngelect everything else in your life and devote your soul to the stupid thing. Nothing wrong with that, I hasten to add.
Amusing review of Guitar Hero III:
http://www.escapistmagazine.com/articles/view/editorials/zeropunctuation/2716-Zero-Punctuation-Guitar-Hero-III
Don’t give up, I was horrendeously bad on easy, but can now “perfect note” 2-3 songs (some songs are way easier than others). I am now dipping my toe into “medium.” The addition of the blue notes are tough. A couple of things I wish I had done from the beginning: learn to strum down AND up, pay attention to the notes that are “white” on top, you don’t have to strum them (just move your fingers on the notes). I am having a lot of trouble getting used to those (since I never noticed them in the beginning).
My favorite song is probably Paint it Black or Lay Down!
When watching the game I always thought wow, that is so freakin’ easy, why does any one play it?! What I was watching, however, was people playing it on easy at parties. Anything beyond easy is actually rather difficult. It takes some practice, and there are definitely some tricks and skills to learn to play the game better.
I can play most songs on medium with maybe two played successfully on hard. My roommate can play everything on hard and most on the hardest setting. I still don’t know how he does it. To any one watching his fingers you’d assume he was just mashing away at the keys, but he nails them. And even when he messes up, he’ll catch right back up without a hiccup.
Care to share any of 'em? 
IMHO the easy songs on Guitar Hero I are more fun: I Wanna Be Sedated, Infected, I Love Rock n’ Roll. And Smoke on the Water which I have a grudge against but still.
For awesomely medium-style fun, purchase the bonus song “All of This” by Shaimus. It’s practically a chord tutorial!
Here’s the tactic I used when learning the game. When you’re playing through a difficulty level for the first time, hoard your star power. Star power makes missed notes penalize you less and hit notes reward you more. It can be the difference in finishing a song or failing. If you get down into the red on a song, activate star power and limp your way through the tough portions.
Once you’ve beaten a difficulty level, go back and replay songs that gave you trouble and try to get a higher score. Eventually you’ll start getting 4 and 5 star ratings on several on the songs. When you’ve 5 starred several on one difficulty level, bump it up to the next.
Don’t be surprised if you improve in bursts. You might go a few days seeing no improvement and then suddenly you’re tearing up songs that used to give you trouble.
Keep in mind also that GH3 is by far the most difficult of the three. It doesn’t seem as friendly to newcomers as GH2 was.
Mostly it’s just about practice. When I started (with GH2), I was failing songs on Easy. Time and practice got me to the end. I thought that there was no way I’d ever be able to beat the game on medium but now I can beat most of the songs on expert.
When you’ve practiced enough, you no longer have to think about where your fingers should be. This is just like being excellent on a real instrument. A beginning guitar player will be thinking, “Okay… C chord. First finger goes here… Second finger here… Third finger here…” Every chord change is a laborious process that requires the active participation of your brain.
After a while, your fingers just go where they are supposed to go. Then you can concentrate on other aspects of the music.
I started with Guitar Hero I, and I was failing songs on easy as well. Now I can beat just about all the songs on Expert (except for ‘Through the Fire and Flames’), and five star 3/4 of them. I don’t even think about where my fingers are - it’s mostly about getting into the ‘zone’ and staying there. When I make mistakes, it’s usually things like just getting my fingers tripped up or missing a note while I’m trying to activate star power. There are still some insanely fast passages in some of the harder songs that my fingers just can’t keep up with, and I don’t know if I’ll ever be able to do that. At some point you just hit a limit of innate ability, I think. My muscles just won’t twitch any faster.
A couple of hints for moving up in difficulty:
Learn to alt-strum. I still suck at it, because I downstrummed only for a long, long time. But the super-fast passages in the harder songs just scream for alt-strumming. Also, you won’t wear out your strum hand as fast if you can do that.
Learn to hammer-on and pull-off. I’m not sure if you can even do that on easy or medium, but a good practice is to always use a hammer on with a note that shows you can, even if you want to strum it. Get in the habit of hammering on and pulling off where you need to - later solos really demand that you be able to do that to beat them.
When you get to the level where you have to hit the fifth button, learn to shift your entire hand without changing the relative position of your fingers. Shift your hand from the elbow by moving your entire forearm. If you just flail your fingers around, you’ll find them out of place a lot. Watch a real guitarist move his hand around the fretboard and you’ll see what I mean. it almost looks like a mechanical movement.
There are some cases where it’s better to just stretch your pinky to hit that fifth note, so you’ll want to learn that technique as well.
Most of this applies to the hard and expert levels. To beat easy, the best advice I could give is to just continue to practice. You’ll adapt and get better quicker than you think.
I don’t have GH III, but on GH II I have a dream that I will one day 5 star on Freebird…On medium…I don’t even want to see that one on harder levels.
Done it. Multiple times.
Darn kids these days. 