Nichijou: Mai wins a stair-climbing game with a spell of restoration, as in a password for the early Dragon Quest games. She later tries to start up a game with it, only to realize she misremembered it.
Time Stop Hero: When Kuzuno Sekai dies and is revived, Shinra says, "Death should not have taken thee." This phrase happens whenever one dies in Dragon Quest.
The World God Only Knows: The second season anime starts with entering a password which allows a recap of the first season. This is all rendered as a Dragon Quest game.
Yakuza 0, which takes place in Japan during The '80s, has a substory where you have to track down a child's stolen copy of "Arakure", which he'd only just managed to buy. This entire substory is a direct reference to the mania surrounding Dragon Quest III in Japan around the time it came out, with people getting mugged for their copies.
Yakuza: Like a Dragon has the protagonist, Ichiban Kasuga, who is a huge Dragon Quest fanboy. He references the series directly by name multiple times throughout his adventure, and claims to see complicated situations in Dragon Quest terms.
to the Hero, Princess Gwaelin and the Dragonlord from Dragon Quest, respectively.