Actually I can envision Seattle, I used to live there...however it would be a lot like gta3 because you have the downtown area, then like south seattle (subburbs),and seatac airport. - the only thing that would be fairly neat would be the shitty cars that can't make it up the huge hills, and the speed you would pick up going down them. -throw in some clogged drains after a few rains and you can have like 4-5 ft puddles on intersections.
Toyko would rock, I liked that idea, but as for the comment about being easy because it's small... NO FKN WAY! that place is massive.
on the subject.....PARIS! think of like ronin, the transporter, or frantic. plus there can still be a lot of mixed races.