NJ5 on 21 February 2010
Ubisoft said there were 450 people working on AC2:
http://kotaku.com/5260424/assassins-creed-iis-team-has-tripled
I know it was probably not full-time workers, but I highly doubt this game had an average budget.
My Mario Kart Wii friend code: 2707-1866-0957