Ive been playing through Phantom Hourglass for the NDS and once you get upscaling up and running the game actually looks pretty good! I put together a video showing native gameplay vs 6x resolution and it legit looks like a 3DS game.
Im always suprised at the level of detail some of these older DS / 3DS era games have in them. The animators made some pretty impressive models only for them to e held back by the resolution of the panels on the devices.
Overall I havent been enjoying PH as much as some of the other handheld Zelda's but its been fun playing a game that I never played back in the day. There are some genuinely interesting puzzles, as well as some frustrating reoccurring mechanics.