The two best I've had:
Grew up with a Maine Coon cat, he lived a long time and was tough, very friendly, playful and followed us throughout the woods. Even on long hikes. He'd even check on me when I injured myself.
Currently have a Norwegian Elkhound dog. She's been a perfect companion. Happy to fly in my plane, excited when she sees the runway on descent, and especially happy when the FBO golf cart comes out! A great hunting companion, play companion, goes everywhere, loves everyone.
Without a doubt, the dog is a better companion though. Any activity from wading in streams (won't swim in the ocean), to long distance all weather walks, communicating her needs, and general intelligence.
Not my cat, but quite similar: