For new users in my opinion there are 2 to 4 options.
The Valve Index as an all around premium kit. It has a high resolution LCD based HMD that can go up to 144hz (though you’ll be hard pressed to find the PC hardware to play demanding VR games at that framerate), it offers a physical IPD (interpupillary distance) switch to match your eyes, it uses the same impeccable lighthouse tracking solution they pioneered with the Vive using 2 base stations you have to plug in a power outlet (with no connection to the PC necessary) and arrange in a way that covers the whole room, and the famous controllers that offer the usual assortment of buttons, analog sticks, trackpads and finger tracking thanks to proximity, touch and force sensors.
The Oculus Rift S which normally costs less than half what the Index does. The HMD uses a single LCD screen so the IPD is handled by software which isn’t as effective in edge cases, the screen only goes up to 80hz, the controllers lack extensive finger tracking as only your index and thumb can be tracked by which touch-sensitive control/trigger they’re over (or none, which means you’re pointing or doing a thumbs up etc.) and the rest, your “grip” with the other 3 fingers, is handled by an analog trigger you press with the middle finger. I’ve sort of focused on the things it does worse than the Index here but I’d say this kit has the best price to quality/features ratio. The controllers were the best for immersion until Index released and the Index controllers alone cost almost as much as the full Rift S kit. It’s a near perfect middle ground. It’s also one of the most comfortable to wear with the halo design pioneered by Sony and licensed by Lenovo with whom Oculus collaborated.
Alternatively to the Rift S and for a similar price you can get an Oculus Quest which has even lower hz (72) yet OLED screens and a physical IPD switch, far worse comfort, but also the ability to work as a stand alone VR console style device with any low end games specifically ported to its mobile chipset. It uses the same controllers as the Rift S and you will need a separately sold high quality USB cable to use it for PC VR games. There’s very slight lag to the controls compared to a native PC VR kit as it wasn’t initially meant for such a feature but if being able to take it in other rooms away from your PC, share it easily, play its (lagless) native games without cables in the way and what not are important to the user it’s a no brainer still. The weak mobile specs do mean it’s likely to miss out on many games, so you will definitely need to resort to using it in conjunction with your gaming PC.
Mostly for Americans, the Samsung Odyssey or Odyssey + which was part of Microsoft’s Windows Mixed Reality initiative. It was once a premium product thanks to its high quality HMD with a physical IPD switch (the only WMR kit to have this iirc) and adjusted controllers (the only company to enhance their build and ergonomics as others used the vanilla Microsoft design) that are similar to, but not as good as, Oculus controllers. The hand tracking isn’t as good as Rift S either but you can get one of these discounted to like 200-250 if you’re in the USA so if you’re strapped for cash the trade off is solid. These things weren’t released in Europe but there are other WMR kits available. You’ll need to look up reviews to see if they’re worthwhile as the quality varies a lot (ACER was the cheapest pos for example yet even that is overpriced in some places, the Lenovo Explorer was ok, etc.) despite the same base capabilities (in terms of controller features and tracking quality) but if you can’t find them for much, much lower prices than a Rift S I’d say it’s not worth it.
I can’t recommend HTC/Vive products now. They’re still good for previous owners as they used the same tracking technology as the Valve Index so they can upgrade to the Index controllers to replace the obsolete, clunky Vive wands but for new users it makes little sense to not go full Index right off the bat. The Cosmos line has better controllers matching the design of WMR/Oculus for the most part but the tracking quality so far has proven far, far inferior which means it’s not worth looking at regardless of potentially better screen specifications. Cosmos Elite goes back to lighthouse tracking but also the wands.
If HTC had updated controllers for their lighthouse kits they would be worth looking into. You could look into mixing and matching parts, a Vive or Pimax premium high resolution/high fov HMD, Index controllers, base stations from any company that sells them (whether v1.0 or v2.0 makes little difference for a home user), but it seems like more hassle than it’s worth over getting a full Index kit.
I myself have the original Oculus Rift with an extra tracker for 360/room scale VR (it came with 2 out of the box which were mostly for front-facing VR similar to PSVR, but with way better tracking, the outdated Move Sony chose to retrofit for PSVR sadly handicapped it heavily). I don’t see a reason to upgrade yet. It was a hassle to set up and needed a lot of USB ports so it would make no sense for new users compared to newer products but it’s not something I need to redo often (and it’s quick for me now that I know it well). It offers great tracking quality, slightly better built controllers than later Oculus products which revised them, 90hz OLED screens with a physical IPD switch, etc. Comfort is so so. The main drawback is the resolution but I need to upgrade my PC to handle higher than that anyway, I will probably do that some time this or the next year and then in another couple years I could see if any company offers a considerably better VR kit for a modest price similar to what I got this for back then. Perhaps an Oculus Rift S 2 or Oculus Quest 2 (which could well be one and the same, as long as the PC connection for the latter is native and not streamed over USB this time) or a hypothetical Index Lite or new competitors.
Games are available in stores like Steam, Viveport and the Oculus Store. Developers tend to use the SteamVR/OpenVR api so they’re often compatible with all hardware. For Oculus there’s the Oculus SDK, usually available only on the Oculus store version but some times also as an option on Steam releases. Regardless SteamVR/OpenVR can handle Oculus products on its own just fine so it’s not necessary, some devs only do it because some users report better performance with the Oculus SDK. Older or new but probably not high quality VR games might only support specific kits (always listed in the Steam pages) but you can often make do with some control rebinding to map your own device’s inputs as corresponding inputs on the devices they do explicitly support. Hand angles and such might be off in this case. Either way, it’s not a problem for most well produced games. WMR kits are the least likely to be explicitly supported as they sold the least, unless Microsoft does anything to revive interest in the initiative. The Oculus Store only works with Oculus hardware officially but there’s a fan application, Revive, for other devices to be able to use it and therefor get to play some of the many high quality VR games Oculus has funded/developed with decent control remapping as long as you have anything better than the Vive wands. Oculus hardware works in other stores and can be expected to be supported for a long time thanks to forward thinking design (the controllers, unlike Vive wands, are still good with compatible layouts and inputs) and the fact it holds like 50% VR market share on Steam, alognside the likelihood more casual users don’t even go on Steam, just Oculus store, plus the Quest has proven capable of selling some games even better than PC and if a game does get a Quest port it’s a no brainer to match it with a Rift/S compatible version.
Native Quest ports are only available through the built in Oculus store and are often cross buy with the PC version on the store. Otherwise when used with a PC it can run games from other stores just the same as any PC VR kit. It also enjoys a very good Wii style homebrew community with a whole unofficial store set up for free releases. In some ways it has surpassed PC VR homebrew as things like Lambda1VR (a Half-Life 1 VR conversion) are superior to equivalent efforts on PC, for now.
With that said it’s a bad period, everything notable is sold out, restocks are slow due to the corona virus, etc. You might be able to find Oculus products in some smaller stores that haven’t marked them up to take advantage of the situation. Index was only really available through Valve so it’s a no go until it’s restocked. Vive products are probably more readily available but a compromise.