Best Sandbox/Free Roam Game

Saints Row the Third

Maybe also Just Cause 2, but there's not a lot of "normal population" in most places.

EVE Online. Spaceships are kinda like cars, right? Seriously though, great sandbox MMO.

GTA 2... i wasted hours burping and farting and listening to radio music instead doing objectives.

Saints Row 2

Saints Row 3(Not as fun sandbox as 2 sadly but still fun)

The Simpsons: Hit & Run

Bully

Sleeping Dogs seems like a nice game, I've only played an hour of it thusfar on my PS3 (thanks to PS+)...

It seems kinda alive and the PC port was supposed to be really good if your PC can handle it

Real World Prime - can't get any more free roam or alive than that, but it can get downright boring as hell with all that realness and shit to deal with...

best free roam skyrim

Fallout

Pokemon.

Minecraft...?

Multi theft auto.

sleeping dogs is what u r looking for, amazing free roam game

Sleeping Dogs.

Minecraft... Saints Row The Third, GTA SA Online, Saints Row 2, GTA 4 Online, Garry's Mod RP, Oblivion, Skyrim...

Space station 13 - as for me it's the best Sandbox RPG.
Mechanics of this game is amazing!

An open world game with people and vehicles, i'd say pretty much any GTA. But sandbox is an entirely different thing.

There are no games like this ATM. The few decent sandbox games out there are not renowned for being heavily populated or full of NPCs and vehicles...

The closest one could be Star Wars Galaxies, and it's pretty dead.

GTA: San Andreas had a multiplayer mod called SAMP, I'm not sure if it is alive anymore though. Had some interested experiences playing that a few years back; Got abducted by some gang on the server and they kicked me out of their limo and pushed me off a cliff. Got my revenge by mowing everyone down with a helicopter blade when I next saw them.

depends. On the sense of do /whatever/ you want (missions in any order, can ignore story, etc) then the fallout series (escpecially fallout 3 in my opinion), Just cause 2, Minecraft, Elder Scrolls games (skyrim). However.... If you just mean any "freeroam/sandbox" (these ones are still free roam and stuff but you can only do so much without progressing in story) inFAMOUS, Borderlands (1/2), Grand Theft Auto.

Minesweeper. If you've never heard of this game, just imagine the gaming version of Hurt Locker. Opened map - you can interact with every part of it from the beginning, permadeath, touching story. You should try it.

I recommend Two Worlds. You may want to skip TW1 as it is quite bugged and the main plot is inferior to side quests (however I enjoyed it greatly! I just repeat what others are saying) but TW2 and the add-on are great.

Free roam : Just Cause,Just Cause 2,Saints row, Saints row 3, Saints Row 3, Skyrim, Morrowind, Oblivion,fallout New Vegas, fallout 3.
Sandbox:Garry's mod
Free Roam and Sandbox: Minecraft (bought it yesterday though ;p) with minecraft you should use Feed-The-Beast mod.