Games work in very different ways. Some are narratives where unless you complete them it isn’t really true to say you’ve fully played them. Others are essentially skill-acquisition challenges - you don’t have to finish Sonic the Hedgehog or ‘beat’ Civilization to be able to say you’ve played them. And others are goalless sandboxes - the Sims or Minecraft, where what you get out of it depends entirely on what you put into it.