Like Zelda, the Yoshi series is quite varied and experimental when it comes to the art style.

Which do you think is best in terms of art direction, and why?

Yoshi's island.
Easiest answer i've given to one of your threads.
I loved the art style much more so than any other game in that list, its so much more memorable. Combined with the soundtrack its just such a good art direction overall. Woolly world would be my second choice, tho I dont think the game is particularly good, the art style is great.

When it was released? Story

Best to hold up for nostalgia today? Island

Best one currently? Hard to pick between CW and WW. They are both so adorable.

In general, all these art styles are beautiful in their own way and so much better than the vast majority of realistic or Pixar clone games out there!

Yoshi's Island. Everything is so crisp and I'm a sucker for well done spritework. The newer games like Crafted and Wooly World do look stunning though.

Crafted was a great looking game, and Yoshi Island was the best Yoshi game, but I liked the design of Woolly World the best.

Aesthetically I really love the original, Woolly World, and Crafted World, and it's quite hard to choose between them but ultimately I voted for Yoshi's Island, although that could be cos I have so much nostalgia for it. XD

Well, Yoshi's Island is one of my all-time favorite games, so it's hard to pick other. But Woolly World is beautiful too.

Woolly world

I don't have much nostalgia for Yoshi's Island, but it's definitely top tier visually for a SNES game. I picked Crafted World, it's just adorable.

Yoshi’s Island SNES.

Nothing comes close to that piece of art. In fact I’d say that is one of the prettiest games ever made in general.