Risks with other potential acquisition partners:
(1) Valve - limited scope. Valve would be fine if Oculus's future were limited to gaming. But they add little value, in balance sheet or experience, for a broader play. Valve + Oculus is only marginally better positioned, for revolutionising computing, than an independent Oculus.
(2) Microsoft - too conservative. Big organisation without a history of funding moon shots. As for pairing Oculus with Xbox, I'd copy the concerns with Valve.
(3) Dell - underinvestment. Dell is undergoing a private-equity turnaround focussed on optimising operating metrics for an IPO. Not a healthy environment for an open-ended, capital-hungry start-up with an adventurous future.
Apple would have been a fine home for Oculus. I suspect VR's market isn't mature enough for Cupertino. But I do not see a material difference between Google and Facebook. Privacy concerns exist at both, and both have a mixed record of integrating acquisitions. What both have is lots of ambition and the surplus capital and experience with which to fuel it.