Ask HN: Simulation vs. Game

Many who are supposed to be serious people insist our universe must be a simulation. (The argument seems, as far as I have been able to discover, to be "because how could it not be?")

My question is, is there any meaningful difference between a simulation and a video game? I can't discern any. So when somebody says we are in a simulation, what I hear that we are all NPCs in somebody's game.

Because, how could we not be?

To the Greeks, the world was the gods' playground. To (certain) Elizabethans, the world was a stage. To the Victorians, the universe was a clock. Every culture imagines the universe is whatever the hell they think they invented.

Are we NPCs?