The other cat's food tastes better

This must be a feline parallel to "the grass is greener...."

I feed my cats separately because otherwise Rocket would eat everybody's food and grow into a blimp. Twinky and Mellie are picky eaters and they frequently don't finish their food. But there must be something about eating another cat's food that makes it taste better. Because when they don't finish their own food, I can put them in the other cat's room, and they'll finish off the other cat's food, even though it's exactly the same food they didn't want to finish off in their own bowl. :

Very very normal.
My dog doesn't like to drink out of her own bowl at the dog park, but she likes everyone else's. It's an animal thing.

My mom's vet said that (with dogs, at least) it's partially an attempt to assert dominance over the other animal. Along the lines of saying, "I'm in charge here, and I'll eat your food if I want to!". At my parents house, both the alpha dog & the cat drink out of the puppy's water dish- just to make sure he knows he's at the bottom of the totem pole!

Before one of my parents' cats died, they had one who was a picky, slow, couple-bites-every-few-hours eater, and one who is overweight that will eat everything in sight. They had to feed them on a schedule in separate rooms, and couldn't really free-feed. It's a pain, but was best for both of them.

Good luck!

I always have several different foods (like a buffet) around the house that are suitable for all of my cats.

My cats just love variety.