At the end of Inception, the spinning top leaves ambiguity about if Dam Cobb is finally in the real world. It led to plenty of debates about what the ending "meant." For Brendan Keogh at Unwinnable, the lack of resolution itself was significant.
But the whole point of that final scene – or indeed, the whole film – is that we can’t know any kind of objective truth about the world, that we always only know the world subjectively, constructing it with our senses even as we perceive it. When Cobb sees his kids, he doesn’t wait for the spinning top to fall because he realizes it doesn’t matter. Reality is what the mind perceives through the body. Sure, there might be some objectively ‘real’ world Out There beyond our own bodies, but we’ll only ever perceive it through the prejudices of our senses. We never, not in a day of our lives, get to see if the spinning top falls over or not.
Similarly, for videogames, we never objectively know their worlds. Some games, like Spec Ops: The Line and Mark of the Ninja make a point of game characters not knowing what's real in the game world.
There is no right decision to make at the end of Mark of the Ninja or Spec Ops: The Line because I simply don’t have access to an objective truth to make such a judgement. There is no truth. The objective realities of both Mark of the Ninja and Spec Ops: The Line, encoded into the hard data of the games, are themselves subjective – unstable, contradictory, unreal. More so, the games make sure I know that I know that I can’t know the truth. They show me the spinning top, and then they snatch it away.