You should have included Fallout3, Oblivion, Farcry 2, Assassins Creed 2, they are all sandbox by definition. I spent the most time with Oblivion, if that determines which one I liked best, followed by Fallout3. I just finished Farcry2, I thought it was great but needed some major tweaking, AI was dumb at some things (a guy in opel would ram your truck w/top mounted machine gun/gernade launcher, not too smart. And EVERYONE wants to kill you, ram you with their vechicle, no questions asked) and smarter at others ( they knew how to take cover, flank, fairly well). The graphics, and the flamethrower were fantastic. I'm still playing AC2, it's looks to be one of the best also. Haven't played Infamous.