I've never really played the games, but I catch a lot of the cartoons when my kids watch them.
I've noticed that I never see any regular animals in the cartoons; only pokémon.
So my question is, do regular animals even exist in the Pokémon universe?
Are they ever seen directly in the cartoons?
Animals are mentioned many times in the series as documented here. These are usually just mentioned in passing or indirectly. The main purpose of real animals seems to be for food for humans.
In this video around the 3:45 mark you can hear Brock and Ash advertising
french-fried flounder, seven-layered crab cakes, squid on a stick, and clam juice snow cones.
Also, here is Ash dressed in a cow costume.
Looks like you've been answered, but I would add that - to my knowledge - the Pokémon actually seen are usually bugs or fish, and references to larger, more complex animals are from the first season, where they were going with the idea that Pokémon was set in the real world. After a while they veered away from that and started saying instead that it was its own world, and the references to animals stopped.
