I think it relates to 90's punk rock (a.k.a. the type of music Green Day does) where they're kinda saying that the punk rock scene has dried up and they feel like they're the only ones left. Like the independence movement among teens of the time had died as those teens grew up and became adults and moved into mainstream society like everyone else had. With it the music they listened to died as well or the bands sold out and went mainstream. So now Billie's kind of saying that he feels like the last gang in town, because all the losers (everyone else) can't even win for losing (sold out or died off), and everyone who's just joining the scene now is only doing it because it's cool, not because they actually believe in the same things.
I think it relates to 90's punk rock (a.k.a. the type of music Green Day does) where they're kinda saying that the punk rock scene has dried up and they feel like they're the only ones left. Like the independence movement among teens of the time had died as those teens grew up and became adults and moved into mainstream society like everyone else had. With it the music they listened to died as well or the bands sold out and went mainstream. So now Billie's kind of saying that he feels like the last gang in town, because all the losers (everyone else) can't even win for losing (sold out or died off), and everyone who's just joining the scene now is only doing it because it's cool, not because they actually believe in the same things.