I saw a post on Reddit claiming that someone recently developed a fork of the Nintendo DS emulator DeSmuME that can render games in higher than native resolutions. As I've never seen a DS emulator do this before I thought I'd test it out and take some screenshots. They don't scale up quite as nicely as PSP games or more recent consoles (as expected) but some games don't look half bad.
Dragon Quest IX: Sentinels of the Starry Skies
Elite Beat Agents
Golden Sun: Dark Dawn
Kingdom Hearts 358/2 Days
The Legend of Zelda: Spirit Tracks
Metroid Prime Hunters
Ōkamiden
Pokémon Black Version 2
Dragon Quest IX: Sentinels of the Starry Skies
Elite Beat Agents
Golden Sun: Dark Dawn
Kingdom Hearts 358/2 Days
The Legend of Zelda: Spirit Tracks
Metroid Prime Hunters
Ōkamiden
Pokémon Black Version 2