What he just said.

I assume you have played Horizon and Zelda already?

A lot of people liked The Witcher 3 a lot, so you should try it if you haven't already.

you play breath of the wild, best open world game since the witcher 3

Xenoblades
Elder scrolls
Fallouts
Witcher 3

Ergh... i see people hyping recent stuff as usual. Let some time pass on those and see what the word is after the dust has settled (and if worth it you can get them on the cheap).

Pick one from Ubisoft and you've seen all from Ubisoft. The most famous examples are probably the Assassin's Creed series (pick any but the first one) and the Far Cry series (FC3 or newer). Skyrim is also a nice choice, even though it's getting old. Personally I also have to recommend Metal Gear Solid 5: The Phantom Pain (but not necessarily Ground Zeroes), even though the game is a bit incomplete. Other than that, I'm not sure I can recommend anything since I haven't played a ton of more recent open world games.

i'm assuming you've played breath of the wild, so

the witcher 3

horizon zero dawn

Zork

Burnout Paradise

Step your game up guys, I've played every single game you guys have listed. :P

Except Xenoblade, might try that out.

Guessing you already played the GTA series, so...
Dying Light
Shadow of Mordor
Gravity Rush series
inFamous series
Yakuza series
...uh, I just played through Saints Row 4, it's ridiculous and fun, worth it if you can get it cheap.
The Reckoning is a fun but simple open world action rpg
.
..
...and that's all I got.

Breath of the Wild (Switch)
Shadow of Mordor (PS4, XOne)
Retro City Rampage (PS4, 3DS)
Xenoblade Chronicles (Wii)
Morrowind (Xbox via Xbox 360)
Far Cry 2 (Xbox 360)
Vice City (PS2)

Good hunting!