Backing vocals on Green Day songs are underrated anyway I think. The fact that he (and the others) can do such great backing vocals in the studio and then perform them perfectly live (where a lot of other, particularly pop punk / alternative rock bands fail) deserves some serious respect. Songs like Holiday, Boulevard Of Broken Dreams, Welcome To Paradise, Minority, J.A.R, Prosthetic Head etc. just wouldn’t sound the same without those backing vocals. That’s also why Green Day is one of the few bands that can pull off The Who’s complex harmonies when they cover their songs.