Green Bay, from an atmosphere, tradition, history, small town, hallowed franchise standpoint can't be beat. The tailgating is much different than it is in Buffalo though. Green Bay isn't just a drunken orgy of human carnage and blue light like Buffalo is. It's a little more dialed down. Every year when that "best tailgating cities" article comes out ranking Green Bay above Buffalo, I laugh a little. From a pure tailgating intensity standpoint, Green Bay is a 6; Buffalo is a 10.
I've been to 15 stadiums and nothing- in terms of tailgating- compares to the greatness that is Ralph Wilson Stadium- clearly I'm a bit biased.
FWIW- The worst is Oakland. chitty stadium,; chitty atmosphere (unless your face is painted silver and black); chitty fans.