well if facebook was ONLY doing VR I would say go for it, but facebook stock is already kinda expensive $110 a share. (Apple was around $20 now ~$100) And investing in HTC might be a REALLY bad idea until they 100% dedicate themselves as a VR manufacturer, their smartphone market if you haven't heard isn't doing so hot right now and may become a liability in terms of total company value (important in regards to stock prices). They are also only one of the the main players, but yet to be seen if they will appeal to the main portion of the initial or future markets. OTOH, their price is low $75 a share and has potential to rise significantly, but I would wait to see the initial feedback from their end device sales price. They might just price themselves out of the consumer market while being a corner case for an already niche market.
Valve isn't public which really sucks (I would have put lots of money into valve some time ago if it was possible)
Samsung (the underlying display's themselves) might be a good investment anyway, but they are just so damn big and got their fingers in EVERYTHING that their success or failure in other areas will likely impact the stock price way more than selling 100's of millions of VR display panels.
Sony and google have the same problem as the rest of them. Too damn big to pinpoint VR's market effect on their total value.
Even if you're not a big fan of PSVR, it might be the safest bet. They will likely sell lots of headsets, and of the entire field, they have a high chance of this not completely ruining them if it doesn't just take off and have the underlying technology of the playstation 4 which won't be highly impacted on PSVR's success or failure, but I see it being successful for them (even though I won't be buying one). Also as of this post $22 a share.
So depending on how much money you want to invest, I would consider the options, HTC risky, more expensive in comparison to sony, less expensive than facebook. Sony, safer, cheaper. And facebook, most expensive, probably safe investment, but less initially impacted by VR's success.