Horizon: Zero Dawn is one of this generation's most breathtaking open world experiences. Featuring a vast open world and a unique science fiction setting, Horizon Zero Dawn managed to steal player's hearts with its amazing cast of robot enemies and a story that will suck you right into it.
The density of the map is really what stands out.
I think that as long as the experience is amazing, which it was then size doesn't matter
Open world does not mean quality. Size does not matter:)