For hiking OSM blows Google out of the water. I'm surprised how detailed OSM is with random forest trails and shortcuts, resting spots, viewpoints, etc.
The main thing I use Google Maps for is searching for stores etc in cities. I hope such information becomes easier to contribute to OSM.
Perhaps a Pokémon Go style game for map updates could work? StreetComplete[0] is good, but the rewards are kind of boring.