I certainly wouldn't argue that it wouldn't improve the city if it were more "lively". But i think it may be a question of what is possible while maintaining image/texture quality, frame frates, animations, etc.
Ignoring limitations, I think it'd be really nice to have people poking their heads out of windows and cheering you on
to swing by a building and see a get together of friends/rooftop dining. To walk down the street and see a garbage truck emptying a dumpster, to swing by Times Square and see a sea of people trying to get their faces on camera during filming of a news/tv show.
But again, there are major limitations to what can be done. I think people grossly underestimate the time, energy, man hours, and processing power needed to get a truly GREAT Manhattan in a Spidey game without having to sacrifice anything. In a few years when, hopefully. But not this generation.