Well, this doesn't necessarily solely have to be a VR game idea, but it couldn't hurt. I'm thinking of a series of fully 3D first person open world RPG games that all involve the player being a monster of some sort, and the main gameplay is being that monster as closely as possible, strengths and limitations attached (though eventually overcoming the limitations is allowed).
For example, say a zombie game. You'd start out as a simple slow, weak zombie that can't run, and you have to hunt down humans to eat, and as you do your ability to survive and hunt improves. At first, you're far too slow and weak to effectively catch anything, so you have to avoid armed prey and either have to sneak up on prey, lure prey with bait or sounds, or play dead and hope that the prey mistakes you for a corpse and gets close enough to attack. Then you have to attack by grappling the prey and holding on to the prey by pushing buttons in the opposite direction of the pulling away the prey is doing and keep biting it until it dies, or attack with strikes and weakening and/or knocking down the prey to make it easier to catch and kill. As you keep killing and eating prey, you get stronger, faster, and smarter and can afford to try taking on armed prey and gradually become able to use simple tools as weapons and manipulate the environment including building simple traps, and by the end of your advancement (a REALLY REALLY long time) even be able to use firearms and body armor. Another mechanic I came up with is the fear mechanic, where you use noise, shadows, traps, whatever to mess with your prey in order to scare them as much as possible, making them panic, slip up, run into a trap, accidentally and/or recklessly use up their ammo if they have a weapon, run into more zombies, etc. but most importantly the more the prey is afraid the more the meat is "sauted" and thus the more nutrients you get out of it eating said prey. The more you mix up the means the faster and more consistently their fear goes up, which is an invisible mechanic you can only determine by the prey's behavior and their lines.
There would be games based around werewolves, vampires, etc. that run along similar lines, games designed to really make you FEEL like you're that monster.