Most popular VR is probably the HTC VIVE, with oculus rift at 2nd. Oculus has been getting into hot water with trying to buy up exclusivity and i warn you, any dev that takes up their offer have been getting a LOT of hell from gamers so i wouldn't recommend it.
Oculus has been trying to force a product/game exclusivity to THEIR vr headset which as you know amongst pc games is not cool so keep that in mind.
There is also the GEAR, the Playstation VR coming, Google Cardboard (both gear and google cardboard use smart-phones? i guess)
Safe bet since its on PC, the HTC Vive would good since all vives come with the two controllers, the oculus is meant really to come with an xbox one controller so in that respect you can assume everyone with oculus or vive will have access to a controller of some sort or keyboard. Vive uses two motion controllers a bit like advanced wiimotes. If you wanted to do VR you should include at least for now 3D modes to make the 3D area curve.