Half-Life: Alyx is mostly what I hoped we’d get from HL3, inasmuch as it hits your points a & b for sure, and IMHO c (though I know that’s not agreed on by everyone). It had great action and expository setpieces (avoiding spoilers), and the (albeit relatively simple) puzzles definitely added something to Half-Life that really worked for me.
Unfortunately it didn’t solve all VR issues (melee being an obvious one), and not least of which the cost. I played it on a cheap (~$100), janky old WMR headset, but not everyone can do that without vomiting, so a great PC and good headset are a hefty price, which is probably the biggest hurdle for a full-scale 3 in VR. Especially considering there just aren’t many other games worth making that investment in, IMHO. I played the hell out of Alyx, a little of a few other games…but Alyx was the pinnacle of what VR could do for me.
Alyx was incredible though! Way more than a tech demo (though I get the argument that it was a test to see if folks would pick up a VR Half-life 3). I played it on a cheap, used WMR headset and an old PC that could barely keep up, and it still stays in my top five videogaming experiences.
It’s a great example to bring up though, because I’d bet it wouldn’t have been made if the studio was only chasing money instead of trying to innovate.
Personal favorite from the era: X-Wing! There were plenty of better Star Wars flights sims in the years after it, but the original on floppy disks holds a special place in my heart.