In the niche area of VR fitness, I think the Quest 2, or the Quest 1 for that matter, was already there. It is the killer app...but maybe the only one for those who use the Quest that way: this morning I did 45 minutes in FitXR and another 25 minutes in BeatSaber, I have a few other fitness apps I use sometimes but I've never even explored the gaming aspect of the system. I don't want to go back to the way it was before the Quest 1 came out, gyms aren't that convenient for me anymore and everything else I could think of to do at home wasn't cutting it.
DDR was as really great fitness app back in the late 90s, early 00s, similar experience, but it required insanely expensive hardware if you wanted to do it at home at any decent quality (rather than just a novelty for a few parties). The Quest has none of that problem (though most of your work is in your arms rather than your legs). It is also too bad Microsoft didn't go the fitness route for Kinect, that worked fairly well also in getting sore at least.