I've played Impulse a few times in the last couple of days and it definitely deserves its spot in the list, if not higher. Also, I think if I was making a list based solely on what I've played, I'd put Gemini and Less Talk More Rokk in there somewhere (taking out Freebird and the song I haven't played).
Question for LD that only includes GH2, Encore, GH3, and Aerosmith: What would you say are the top five co-op songs?
Second question for LD for the other three games: Top five bass, drum, and vocal parts?