Racing games are generally pretty awesome, but I haven't touched them.
I would vote The Legend of Zelda: Ocarina of Time 3D for graphics, as Resident Evil: The Mercenaries 3D has jagged looking zombies from a distance that move jerky (and the timing to snipe them is even worse).
Steel Diver looks good for the 3D, though during the periscope missions it interferes with gameplay.
Pilotwings: Resort gets my vote for 3D, as it's the only game I've played where it really felt like an enhancement. --- Please do not feed the trolls, mark & move on. Likely posted from my 3DS.