I'll have to go with Freedom City too. I liked it so much I created the WSAR Newscasts for use with it (you can download the mp3's at the downloads page of Valdier's Site - plug, plug ).
Well, I agree with what others here have said, but once you get Freedom City (and maybe Crooks), check out The Algernon Files by BlackWyrm Games. It's a great source for heroes and villains of all sorts.
I'd have to go with Freedom City, too. Greatest M&M supplement out there. Crooks! is good, too, but I don't like most of the art (Ramón Perez should have handled ALL of the art on that one).