Saints Row The Third did the best at giving you a big open city where you can do whatever the f*** you want with no restriction. I also liked how the police were a bit more laid back then GTAIV where you can't do anything fun without cops coming after you, like you couldn't even start a fist fight without a cop spawning from nowhere to jump you. I also like how they made the flying vehicles more fun to use than in other sandbox games. Helicopters still suck to drive but something like the V-TOL is awesome, you can switch from an easier to aim but slower moving mode to breakneck speed. There were also a bunch of tough areas set up for you fly through and you get double the respect for pulling it off upside down.