There's a bunch of VR games/apps that are notable for fitness. Beat Saber is the most well known one that's explicitly a game, Supernatural is maybe the most famous one that's framed as more of a fitness app/service.

But other notable ones include Synth Riders, FitXR, OhShape, Pistol Whip, Thrill of the Fight, and (maybe) Gorilla Tag. And this list is far from exhaustive.

VR is pretty good for fitness just because it can make exercising more interesting, comparable to sports without the need to coordinate with other people (and it's easy to do inside your house, if you have at least a 2m x 2m open space). Major downsides would be having that space available and sweat inside the headset.