According to my taste:

1st - 5

The colors used in the artwork are very pleasant on the eyes. The light blue makes you feel like you're at a beach on a warm sunny day.

2nd - 1

There's a lot going on in the picture. The various characters are engaged in a unique action.

3rd - 4

The intricate details are what make this image one among the top 3. The shading done in the center gives it a 3D look.

Thank you @kalemandra for hosting this challenge. :)