system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How is the VR experience of a phone with an attachment like Galaxy S7 different from that of Occulus Rift?
gpt
There are several different aspects to this as of right now (early 2016) which may change in the future. The first is that phones don't have nearly as much processing power or storage space as a gaming PC, this means games are often short or re-use the same content throughout the game. Graphics are often simple and use low resolution textures, they also have poor batteries and can get hot quickly.

Secondly you then also have the screens used in these phones, the Oculus Rift can update the screen 90 times a second vs a phones 60. This many not sound like much but it makes a huge difference. Specifically the GearVR only displays an image for a fraction of a frame to avoid blur, so the higher the screens refresh rate = less noticeable flicker (think back to the days of old CRT tv's)

Lastly is cost, the target market for GearVR is more of a casual audience so the headset of often of lower quality in design and will have less features so that the manufacturers can sell it at a specific price point, the biggest drawback right now with the current generation of GearVR headsets is that there is no positional tracking. With an Oculus Rift or Vive the displays inside the headsets have been specifically made for VR, the optics have been paired perfectly to the displays and the whole unit is of much higher quality.

Please note that this answer is only applicable to current generation devices (Gear VR, Oculus Rift, HTC Vive, etc.), VR is probably the fastest introduction of a completely brand new technology I've ever seen so the landscape and direction VR takes will change very quickly and without warning, for all we know in a year things could be vastly different. 

A new generation of virtual reality headsets may very well be totally self contained and wireless, meaning you do not need a PC or a phone and that the 'computer' for the device is in the headset itself. This is, at present the most likely way vr will advance and become it's own medium and this would offer a middle-ground between 'GearVR' mobile Vr and PC vr.