Great question — answering as the UphillTech team:
The Dragon's Lair game doesn't have to do with Will or the demogorgan this time, but with the love triangle of Max, Lucas and Dustin. We see Dustin playing this game while Lucas, Will and Mike watching. When Dustin loses this game, following conversation takes place. Lucas: You're not nimble though, but you'll get there one day. But until then, princess Daphne is mine. Though, Lucas was referring to the video game, but it also predicts the outcome of the love triangle of Max, Lucas and Dustin. Source
Full answer by A J: https://movies.stackexchange.com/a/82362 (CC BY-SA 3.0).
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