I like Toxicity from guitar hero Metallica. I'm not that good, and I'm only playing on medium, but that song's fun to play. I also like No Excuses, it's not that fun to play but I'm a huge fan of AIC so I play it a lot anyway.
Pull Me Under - Dream Theater from Guitar Hero: World Tour. I just really liked the opening to that song, and the rest was good too.
I despised that song. It goes on forever.
GH2: Sweet Child O' Mine.
Great intro and solo.
GH3: Cliffs of Dover
Pretty complex but a lot of fun once you get a hang of.
GHWT: Love Spreads
Somewhat underrated, fairly easy, but a hell of a lot of fun to play. Needs a decent solo though.
GHM: Enter Sandman is a lot of fun to play, as is One, which I like the way they've changed from GH3. For pure fun though I'd go for Sad But True. It's just so BA.
Pretty complex but a lot of fun once you get a hang of.
Took those words out of my mouth Fire Fly. I also want to add Iron Man from GH1 and What I've done from GHWT. Even though WT songs are waaaay too easy, still love Linkin Park.