Mario Kart 8 and Smash are up there for sure. In my opinion, they stand out as the best looking games I've seen this generation (in terms of how visually appealing they are thanks to colour and art). Sure, Mario Kart has some jaggies and whatnot, but it's still a stunning game when seeing it in motion. Smash also looks really damn good and is super crisp thanks to 1080p, however in close-ups it definitely loses a bit of detail. Stuff like that doesn't personally bother me though.
Also, you really can't go wrong with Wind Waker HD. The original game was (and is still) stunning visually thanks to the smart art-style choice. I think the HD version of the game looks better at 1080p than anything Dolphin can do to the original game. That's just my opinion though, I've seen some people say otherwise.
EDIT: Ah, how could I forget Mario 3D World!? That game also looks damn good. Just a joy to look at, and of course, a joy to play as well.
Also, you really can't go wrong with Wind Waker HD. The original game was (and is still) stunning visually thanks to the smart art-style choice. I think the HD version of the game looks better at 1080p than anything Dolphin can do to the original game. That's just my opinion though, I've seen some people say otherwise.
EDIT: Ah, how could I forget Mario 3D World!? That game also looks damn good. Just a joy to look at, and of course, a joy to play as well.