I have to disagree somewhat.
Wizard of Oz: Beyond the Yellow Brick Road - Before I saw DQMJ, I thought this game had the best graphics on the DS. It has beautiful visuals, and the animation is well-made.
The World Ends With You - This game has great 2D visuals that add to the gameplay and the story. Everything's so colorful and unique! The animation is top-notch as well.
Chibi-Robo: Park Patrol - The graphics are well-made, and make for a more fun experience.
Okaeri! Chibi-Robo: Happy Rich Osouji - This game has better graphics than Park Patrol! Chibi-Robo looks naturally shiny instead of that forced shine look he had in Park Patrol, and everything seems like the original Chibi-Robo game for the Gamecube, except with the graphics toned down just enough to work on the DS! (This won't count until it gets its US release, though, according to you)
Tales of Dagur - This homebrew game has awesome 2D graphics, even if they ARE in the default set for that Japanese game maker that was ported to the DS not too long ago.
Final Fantasy Gaiden: Four Warriors of Light - This game has the best Cel-shaded graphics on the DS! It doesn't have those awkward outlines most cell shaded games have, which gives it a unique look. The menu graphics are just as beautiful! (This won't count until it gets its US release, though, according to you)