This is a video created by RED SIDE visually comparing the sizes of various large video game maps (previously: another take on the same idea). It begins with the 2.75km² map of Assassins Creed: Unity, and ends with not showing a 31,700,000,000,000,000,000,000km² map of No Many's Sky. Before that is the 4,096,000,000km² map of Minecraft, and before that the 161,600km² map of The Elder Scrolls II: Daggerfall. I learned a lot by watching it. But mostly, it's not the size of your map that matters, it's how you populate what you've got. "Was that a sexual euphemism?" I certainly hope not, because I've never felt less sexy about anything I've ever written.
Keep going for the video.
Thanks to Closet Nerd, who had this to say: "HOLY SHIT BALLS!!!!!!!!", and I'm gonna have to agree.