Metroid Prime Trilogy is definitely a big one since a lot of that game is very dark and it's hard to see the details.
Other than that, most Nintendo games rely heavily on art rather than graphical effects so they look good regardless of whether or not they're HD. If I had to choose then probably Skyward Sword, Twilight Princess, Xenoblade or The Last Story.
Desktop: AMD Phenom X4 955, ATI Radeon 7950 :: Laptop: Intel i7-3532QM, ATI Radeon 7670m
Consoles: 3DS XL, PS Vita, Zelda 3DS, PS3 Super Slim, DSi, PSP Go, PS3 Fat, Wii, GameCube, PS2
Now Playing: Metroid Prime 2, Dark Souls, Fallout: New Vegas, The Legend of Zelda: Oracle of Ages, Persona 4: Golden