It has to be L.A. It's a joke we don't have a team at this point. The second most populated city in the nation with a ton of NFL fans out here.
Lions fans are an endangered species out here though, but there are tons of hardcore Raider, Charger, 49er and Rams fans out here. If the Raiders were ever to win a SB there would be riots out here that would put the riots after the Lakers won to shame.
Tons of bandwagon, fairweather fans you see courtside at Laker games that give the L.A. fanbase a bad name. This city has a lot of hardcore fans that love there Raiders, Dodgers and Lakers.
EDIT: I think Portland also deserves a team before Toronto and London, IMO. Great fans up there going by there support of the Trailblazer and the Ducks v. Beavers rivalry.