The actual intelligence of some Pokemon is debatable, with some absurd outliers like Alakazam or Metagross, but the vast majority of Pokemon seem to have about the same intelligence as something like a dolphin, cat, pig, or dog with the basic ability to understand human speech.

They can't talk, write, or even communicate without animalistic noises or saying their own name sometimes, so for all intents and purposes they are just magic animals. Owning a Pokemon is the same as owning a dog.