Half-Life Alyx is the greatest gaming experience I have ever had the pleasure to witness. I now occasionally VR golf. It's a steep price for a niche with not a lot of games.
HL:A is incredible, and I think it's still the best single-player VR game ever made, but it's almost seven years old now. It's pretty clear that this software ecosystem is dead.
In particular, I don't know if the Steam Frame will have the power for this, but something like a native ARM build of Dolphin (so no FEX) that exposes the 3D nature of polygonal games is very interesting to me. If you can cross your eyes to get stereo you can see what that would look like for something like Super Mario 3D Galaxy here: https://www.youtube.com/watch?v=XmgdqCL2toE (I find a conventional, unfolding phone to be a pretty good size for that. On a big monitor getting it small enough to cross eyes can be a challenge.) In general any emulation target that has 3D polygons is really interesting to me. I'm also pretty interested in what full 3D does to Skies of Arcadia (could be a complete disappointment, could be absolutely amazing) and Sin & Punishment: Star Successor, where I feel like the game that was a bit crowded and struggling with being 2D in SD might just come alive. (Assuming they didn't play too many games with the distance that doesn't work if we see it in true 3D.)
I gather the modding community is already gearing up for modding more games to be true 3D in the VR space. That is, not necessarily VR (though there's a mod community for that as well), but having a visible screen floating in 3D VR space where the screen itself is fully 3D. There is also a wide variety of games from the past couple of decades that I suspect might be very difficult to "convert to VR" but might be relatively easy to trick into rendering full 3D instead of down to 2D.
Nothing really stops any of this from happening now, but I've tried to set it up before and I was unsuccessful with my current stack. Being able to give out instructions that say "Install the Dolphin3D Build from the Flatpak Store and load up your ROMs" rather than the current set of ad hoc complex instructions that I couldn't even get through successfully could be a game changer.
I will giggle like a schoolgirl if the reason why Steam Frames sell like hot cakes in six to twelve months is that they become recognized as the premier way to emulate 3D systems from the Playstation forward. Overclocking, texture packs, modding, all that's great, but how about all those things and true 3D for a lot of games?