[question] Sandbox games

[Vanilla]

Well, besides the ones you've mentioned, there is Fallout 3 and Fallout 3: New Vegas. I've enjoyed both of them.
Then there is the movie clones, which also feature an open world, but slightly more tied to an actual movie, such as Godfather: The Game, as well as The Simpsons Hit & Run, in which you play the simpsons open world, and last but not least: Scarface: The World Is Yours.
Then there is a GTA 3'ish game where you play as a cop (good guys?), True Crime: Streets of LA.
Then there is the always nice GTA clones, which emphasizes a bit more on action and violence rather than realism: Saints Row I & II.
But I shouldn't forget about the Mafia series, the first were a classic and the second is a delight to play.

Then there is also a couple of racing/driving games, where you roam a free world in a car:
Need for Speed: Underground 2 and Most Wanted, Test Drive Unlimited (Recommendable), as well as the old but good Drivers series: Parallel Lines and San Francisco.

Currently, I've begun playing the newest Wolfenstein, and it also features a smaller open world, where you roam a town and have to either shoot or sneak by the Nazi posts. Then you can upgrade and buy weapons as well. Metro 2033 is kinda like this, but in a less open gameplay, where you have to travel the metroes to reach as certain place, and you can buy stuff along the way.

That's all I can think of now.