>>364581163
Probably Skyrim VR or Boneworks.
Skyrim VR will generally get you the most bang for your buck, as it's the VR game I've easily spent the most time on.
Boneworks is overall a better "VR game" and isn't *that* short, but still fairly short and feels a little like a tech demo.
Half-Life Alyx is also good, it's a full-length game but it very much caters to VR newcomers.