While animals come in many different shapes and sizes, there are definitely some that are more intelligent than others.
While you can't directly compare between species, I tried to put them in an approximate order.
At the bottom of the spectrum we have extremely basic creatures, like jellyfish and worms.
While some have simple organ systems, none of them are capable of complex thought and quite linearly respond to external stimuli.
A bit like little robots.
A bit above there we have animals like small reptiles.
These creatures have the fight-or-flight response that helps them eat things or avoid getting eaten.
In humans this is the same physiological response that ruins my PowerPoint presentations.
Farther along the spectrum we have small mammals, like mice or rats, Both capable of learning new behavior and can be trained to some degree, Often used in drug trials as a human analog because of their similar biology and accessibility.
So moving on from there, we have some large mammals, like elephants.
