The most popular VR headsets (aka HMD or Head Mounted Display) in the market today are the Samsung Gear VR, the Oculus Rift and the HTC Vive. The Samsung Gear VR was released in November 2015, the Oculus Rift in March 2016 and this was closely followed by the HTC Vive in the following month.
The Oculus Rift is clearly the leader in the high-end VR headset segment at this moment, trailing behind by the HTC Vive. Both the Rift and the Vive are light years ahead of the Gear VR which does not belong to the high-end category.