This is a matter of opinion. I say 21st Century Breakdown, but that's just me. Their albums are(In order by year): 1039 Smoothed Out Slappy Hours(1990) Kerplunk!(1991) Dookie(1994) Insomniac(1994)...
all of themm duhh.<333
The best selling album by Green Day is Dookie.
1,039/smoothed Out Slappy Hours
American Idiot for Both