From what I played I would say Just Cause 2. The world is just massive and varied. To bad there isn't much to do.

Xenoblade Chronicles (3d) and Zelda a link to the past (2d). I'm sure Zelda U and Xenoblade X will fight for the 1# spot for 3d open worlds later.

I know Xenoblade Chronicles structure isn't exactly open world but it feels like it when you play the game. Everything feels connected, especially the mechonis view in the distance, with a different angle depending on wich part of the bionis you are.

Easily GTA on PS4, just walking down the street in first person looking around and the world is just alive in every corner you look.

Every other larger open world have been fields of fields covered by more fields. Nah.

Xenoblade Chronicles - can't wait for the sequel

The Elder Scrolls IV: Oblivion, i've always been hard to impress and those times weren't our times were an open world game comes out every month, there was San Andreas wich was old but still awesome, there was morrowind of course wich was awesome for its time but that was a 5 year old game and it showed, when I saw Oblivion for the first time when i was there in front of the pc and that opening scene where the camera goes over the world and reaches the city, wow; Maybe from there on great looking open world games started coming more ''steadily'' and that, the fact that sandbox games were scarce, or maybe it was just me who hadn't played a bunch of them at the time, made Oblivion's impact much bigger on me, of course games coming out today are amazing looking but they come out consistently making changes little by little and obviously the impact that they may have, at least on me, is weakened. Oblivion is the most impressed i've ever been with a game world ever, it was the last game that made me say, and i mean it, ''holy shit''.

WoW. Nothing can compare to the awe of playing that game for the first time. The scale was, and still is, unreal.

Uhh..uhh...Minecraft? I don't play and enjoy many open world genres lol.

Another vote for Fallout 3 and Fallout New Vegas. Yes they are a bit grey but with the right mods on PC they look very nice indeed and the game has got huge atmosphere with the right music and uncertainty about what is around every corner.

Hmm, sounds like going outdoors in Norway.

first open world game to blow my mind was GTA 3... and remember this was back when open world wasn't a thing.

My mind was again blown with the original Assassin's creed.

Nowadays open worlds don't impress me because they feel soulless and empty despite being huge.