If someone found a way to play any old game in VR, I'd probably get a headset. All those old FPSes like Doom, Duke Nuke, Quake, etc. would be awesome.
There are 2 methods:
1. 2D virtual screen
2. 3D conversion (ports)
You can play the games on a virtual (flat) monitor in VR using remote desktop:
Connect wirelessly to your computer(s) to watch movies, browse the web, play 2D games or stream PCVR games. Virtual Desktop is a highly optimized, native application developed for low latency, high quality streaming. • Connect up to 4 computers (Windows 10 or 11, macOS Catalina or later) • PCVR...
www.oculus.com
They even have custom rooms, so you can have a 3D VR room with a 2D projector screen that streams your desktop PC screen in 2D, it's pretty cool!
There are also 3D ports available. For example, Vivecraft is a mod for Minecraft that lets you play room-scale (walk around your room) or seated (in a chair) in VR: (I will not be answering questions on how many hours I've spent in this lol)
Virtual Reality Minecraft for SteamVR
www.vivecraft.org
Half-life: Alyx is available in native VR, but there are also fan-made ports for the older ones:
A fan-made highly immersive Virtual Reality mod for the classic Half-Life from 1998.
store.steampowered.com
Half Life 2: VR Mod is a fan-made project, which adds full Virtual Reality support to the original 2004 PC gaming classic by Valve Software. Are you ready to become the Freeman?
store.steampowered.com
HalfLife VR on QuestReturn to Black Mesa and experience one of the greatest games of all times as you never have before in Virtual Reality!This release version is for Meta Quest. There is also a version for Pico.Getting started:What version of HL1 do you need? Buy HL1 on steam and then...
sidequestvr.com
Ports are hit-or-miss because there's a lot of tweaks that go into VR games so that you don't get nauseous playing them (framerate, POV, movement, etc.). Games made for VR are a lot nicer...for example, the guy who made Jet Island did a really fun job figuring out how to get you to hover-surf with grappling hooks on a massively-scaled map with huge bosses and it is SUPER fun for a slow-style game: (I've spent a loooooot of hours playing this one!)
Slide anywhere on your hoverboard at extreme speeds! Explore the massive open world of Jet Island! Learn to skate on any surface, swing from tall buildings, fly in ways you never knew were possible! Defeat the 4 giant boss fights! Get ready to experience complete freedom in VR!
store.steampowered.com