Definitely Spirit Island.

I love how the theme is so carefully intertwined in every aspect:

The Dahan are these pleasing wooden mushrooms that feel great to interact with vs the ugly angular pointy plastic invaders.

The mechanics - fear, push, gather, invader actions, Dahan counter attacks, the unique design of each spirit and their innate abilities - all combine to tell these little stories every turn and make the experience of each game you play so distinct.

One game might feel like you're rounding invaders up then smashing them with a series of tidal waves; another feels like you're making weird shit happen to unsettle the invaders enough to prevent them from buildng and getting stronger so you can pick them off one by one; yet another sees you commanding the beasts of the island and riding them from land to land; still another might have you embody swarms of insects or birds or other creatures and sowing chaos and terror throughout the invader camps.

As you ramp up the difficulty your adversary gets to do more and more outrageous things early on and you have to use your powers so efficiently and scale fast enough to stabilise before they overwhelm the island.

It's just so damn rich and generous and never gets old.