After finishing Red Dead Redemption on Xenia, I have a weird itch to play some more of the open world games I've missed. I was just completely exhausted with sandbox games by around 2013 and avoided all of them, even the ones I heard good things about.
Some of the games on my "maybe check out" list:
Sleeping Dogs - Apparently a really good GTA clone. The Hong Kong setting and melee combat make it stand out.
Assassin's Creed 4 - The two additional Ezio games and Assassin's Creed 3 were big factors in why I got completely burned out on open world games but the ship combat is supposed to be really good- also pirates are cool. It should also predate the series turning into a singleplayer MMO thing.
Far Cry 3 - Never got around to playing this despite all the praise. I know the FC3 style got milked to death but there's probably a reason it became used as a template for Ubisoft games. Wasn't this also the game with the retrofuturistic 1980s DLC campaign with Michael Biehn?
Mad Max - From what I've seen this is a pretty generic open world game in the vein of the later Arkham games but it seemed like a pretty faithful recreation of the Mad Max world in video game form.
The Saboteur - play as an Irish race car driver turned partisan in nazi occupied Paris. Gameplay is mix between 1940s assassins creed and GTA with a cool art style that turns from stormy noir black/white/red to colorful and sunny as you liberate more of the city
That was a bit earlier, wasn't it? Wasn't that also the last game the Mercenaries studio made before they got shut down? Might put that on the list.
(The Mercenaries games being the ones where you blew up North Korea and Venezuela, respectively)