Rune isn't the only one, but you have to keep in mind that the only people reviewing them (I assume) are those who bought them. People like me me who would give Beat Saber a 1 star review simply because we dislike the whole concept aren't going to buy it in the first place and thus not review it. So you really can't compare the ratings between Beat Saber and Robo Recall. At best, you could compare Beat Saber to other rhythm games. I assume they exist, though I don't know of any. Similarly, Robo Recall's ratings can only be compared to other FPS's, like Arizona Sunshine.
I just found out there's a free Racket: Nx demo on Steam - it's a 2GB download. I just tried it and must admit I'm impressed. Like you wrote, which I think is spot on, we should be careful not to mix different genres - and both Beat Saber and Racket: Nx (guess both are sports games to some degree) belong to completely different genres than Lone Echo and Robo Recall. Maybe the lists can help to find games and apps that - within their respective genres - will be extremely impressive. Racket: Nx is not just polished - I'd call that game
ultra-polished. It plays like some weird cocktail of tennis and Arkanoid, but it's an awesome cocktail and trailers don't show this game correctly (like nearly always for VR games). Racket: Nx is easy to access and understand, it performs awesome (even forcing super-sampling 2.0 I get perfect 90 fps and 30-40% extra headroom) and few if any will experience technical difficulties (like the game crashing) - because to get a 96 % average rating you need all users to be happy ;) Still, to me it feels more like a $10 game than a $20 game, but of course the devs got to make a living :)
https://youtu.be/dKcMVUN4RicFor persons who like this kind of futuristic tennis, Racket: Nx may indeed be the reference, but it wouldn't qualify as a top 5 Rift game to me, because I value other genres higher.
Note that Racket: Nx wasn't out of Early Access before July 17 2018, so you could say it's a new game, less than 1 month old (at the time I write this post). Maybe I should try Beat Saber soon like Falken76 suggested - if not for anything else, just to see what a 98% game (based on more than 1,000 ratings) plays like...
