I hear that about Green Day all the time, and I really don't understand it. If you listen to Kerplunk and then listen to Dookie, what's the difference musically? Both are simplistic, but fun pop-punk albums. Dookie contains lyrics about staying in and wanking, its not tailor-made for the radio. After getting massively successful from Dookie, they followed that album with Insomniac, which was a quick, fast punk album that removed a lot of the pop from the album that made them massive. It would have been easy for them to make Dookie pt. 2, but they made the album they wanted to make. American Idiot is also an incredibly ballsy record, they came back after 4 years after the poorly received (but in my mind their best album) Warning with a political album centerpieced by two nine minute multi-part rock songs, completely unlike anything they've ever recorded before.
Green Day are a massive band because they're brilliant, not because they 'sold out'.
I'm genuinely interested in why you think they're sell-outs?
I've thoroughly enjoyed each and everyone of Green Day's releases. I think change was good for a band like them. American Idiot
had the two nine-minuters not Warning.