Neither will mine. (At least not perfectly, all the time.)
But don’t stress about rudeness and defiance yet. There may be a context-specific reason contributing to their unwillingness to stop.
If you’re not a gamer yourself and don’t really understand why being asked to stop is so annoying, consider asking these questions …
Is this a multiplayer game?
(You wouldn’t run onto the soccer field and drag your kid away mid-game. If they’re playing with, or against, other people online, they’re committed.)
When is the next time you can save your game?
(They may have been trying to get to a checkpoint for 20 minutes and are nearly there.)
What are you doing/building?
(They may have a mental list of things they’re trying to achieve before they quit, like to finish constructing a home, or clearing an area of enemies. They could always write a list of tasks for tomorrow, if they worry about forgetting where they’re up to.)
Can I watch you play?
(You’ll get a better sense of the flow to the experience, natural lulls and such. All games have them, and they’re quite different, by genre.)
Alternatively, I often find, “We’re finishing at 8pm,” quite effective – if we agree on a time limit in advance, and as long as they know to save their game and say goodbye beforehand.
Or, I sometimes remind my kids that unsolvable problems in games often fix themselves after a break. I don’t know why, but difficult puzzles in adventure games seem to be easier to solve after your subconscious has mulled them over for a while; tomorrow. Difficult platformers are less frustrating after a break, too.
Lastly, I’m the Gamer-Mum and “let’s finish up” is still a constant negotiation. But, my kids trust me to respect the time they invest into their hobby and I trust them to finish up reasonably, in good time, to eat dinner, go to bed or finish homework.