Here is the top selling list of VR games on Steam.

Boneworks - Unity

Westworld Awakening - Unreal

Beat Saber - Unity

Blade & Sorcery - Unity

Pavlov VR - Unreal

Pistol Whip - Unity

Skyrim VR - Internal

Fallout 4 VR - Internal

Superhot VR - Unity

Layers of Fear VR - Unreal

Zero Caliber VR - Unreal

Moss - Unreal

5 - Unity, 5 - Unreal, 2 - Internal. Depends on a game type you wanna build and perks of each engine.(grants etc)