Which is the best open world game for PC?
The Witcher 3 is probably the best open world, not only of the decade but probably of all time. Also you can point out titles such as Ac4: Black flag and Fallout NV. Back in 2008, Fallout 3 set a new benchmark for what open world [role-playing games] were capable of. We view it with such derision in hindsight, because Bethesda never really moved on from it. Fallout 3 brought the Fallout series into the mainstream.
What is a fully open world game?
In video games, an open world is a virtual world in which the player can approach objectives freely, as opposed to a world with more linear and structured gameplay. Notable games in this category include The Legend of Zelda (1986), Grand Theft Auto V (2013), Red Dead Redemption 2 (2018) and Minecraft (2011). The game features an open world environment that is free for players to explore. It features several environments, including forests, rivers, and mountains.